Thursday, December 27, 2012

Batch cropping images using Mogrify


The command 'mogrify' can crop multiple images simultaneously. Sample case is below.
mogrify -crop WidthxHeight+x+y        images*.png
mogrify -crop 2796x983+429+327        images*.png
The values of width, height, x and y can be obtained by opening an image in Gimp and selecting the rectangle of interest.

Monday, December 24, 2012

Firefox/Thunderbird already running but not responding

Firefox and Thunderbird can sometimes give this error when you restart a linux box or when you try to make multiple log ins into a shared file system. The result is that Firefox/Thunderbird will not open. The causes for this are not entirely clear to me but I found a solution. Simply delete the .parentlock file in both cases and restart the service. Locations for this file are as follows:
Firefox: ~/.mozilla/firefox/xxxxx.default/.parentlock
Thunderbird: ~/.thunderbird/xxxxx.default/.parentlock
Since both the folders and files start with a dot, they are not visible with a simple
ls -lrt
You have to use
ls -lrta

Saturday, December 15, 2012

Emacs Primer

I decided just a little while ago that it was time I learned how to use a text editor other than vi. Below are my notes as I keep learning more about Emacs.

Open a new file: emacs newfile.txt &

Starting writing in the file.

Save: ctrl x s
Search Forward: ctrl s
Search Reverse: ctrl r

Exit emacs: ctrl x c

Select Region:      ctrl space and arrows
Mark Activate:      ctrl space
Mark Deactivate: ctrl space or ctrl g
Select All: ctrl x (wait) h

Delete Region: ctrl w
Copy Region:   Esc  w
Paste buffer: ctrl y

Delete till end of sentence: ctrl k

Delete line: ctrl S backspace

Delete next word: Esc d

Undo last action: ctrl _ (underscore)

Jump to end of file: Esc >
Jump to start of file: Esc <
Go to line 10: Esc x 10   

List all buffers: ctrl x (leave ctrl) b

Split screen:                                   ctrl x (leave ctrl) 2
Close all but current buffer:     ctrl x (leave ctrl) 1
Close only the current buffer:  ctrl x (leave ctrl) 0

Repeat 9 times: ctrl u (leave ctrl) 9
Type - 9 times: ctrl u (leave ctrl) 9 -

If you start a command and then decide you don't want to complete it, type C-g to cancel it.

http://doors.stanford.edu/~sr/computing/emacs.html
http://www.nbcs.rutgers.edu/newdocs/unx01101/unx01101.php3
http://dept.cs.williams.edu/~kim/cs136/s04/emacs.html

Edit: Dec 28, 2012
I was writing a manuscript in Emacs and the bibtex reference key had a beta symbol which meant that I had to type this into Emacs;   Kheterpal2000Aβ and not Kheterpal2000$\beta$. To do this I copied the following two lines into ~/.emacs and solved my problem. Thanks to this site.
(global-set-key (kbd " a") "α") ; F9 followed by a
(global-set-key (kbd " b") "β")
 

Tuesday, November 6, 2012

Latex Template

Reminding myself of every detail in the assigning of packages and page type in Latex seems like a bit of a chore. So I copied the following from a working .tex file to reduce redundancy.

\documentclass[12pt,doublespace]{article}
\usepackage[top=3cm,bottom=3cm,left=2.5cm,right=2.5cm]{geometry}
\usepackage{rotating}
\usepackage{apacite}

\begin{document}
\title{}
\author{
Name
\small Affiliation
\and
New Name
\small Affiliation
}

\maketitle
\begin{abstract}
...
\end{abstract}

\section{}
Main body

\end{document}

Wednesday, October 17, 2012

pdflatex vs pdftex

I have a document with lot of .eps figures embedded in it. These figures were of high quality but also large size. To cut down on the size I converted them to .png which were a tenth of the .eps format. Now using
latex file.tex (with eps figures)
worked well. But to use .png figures I thought I had to use pdftex.
pdftex file.tex (with png figures)
Turns out I should have used pdflatex instead. I ended up losing quite some time on this. The switch to pdflatex did the job and gave me a file which was a tenth of the original size. More on this from here:

"pdftex expects the file to be plain TeX. pdflatex expects it to be LaTeX. These
are two different dialects of TeX. You do not expect a C compiler to work with
Java, do you?

Note that in practice pdftex and pdflatex are often the same command, which
analyzes how it was called to switch to the proper input language. On some
systems gcc behaves in the same way, compiling C if it is called as gcc or
Fortran if it is called as gfortran."

Bottom line, figures can be heavily compressed by converting them to png format w/o a large loss in clarity; and pdflatex can handle png figures. Even if there is a loss of clarity, this is usually just fine for supporting information; maybe not so much for main article.

Tuesday, October 16, 2012

Monday, October 15, 2012

Handling references using BibTex










Scientific journals with arbitrary requirements for reference styles can be a source of great heart-ache. When writing articles using Latex-BibTex, ability to handle reference styles can be useful. These articles are a great starting point to learn more about this:
http://amath.colorado.edu/documentation/LaTeX/reference/faq/bibstyles.html#styles
http://chenfuture.wordpress.com/2007/09/24/diy-your-bibtex-style-file/
http://www.math.washington.edu/tex-archive/macros/latex/contrib/custom-bib/merlin.pdf

Tuesday, October 9, 2012

Controlling axis properties in R

http://www.programmingr.com/content/controlling-margins-and-axes-oma-and-mgp/

The mgp option
In addition to changing the margin size of your charts, you may also want to change the way axes and labels are spatially arranged. One method of doing so is the mgp parameter option. The mgp setting is defined by a three item vector wherein the first value represents the distance of the axis labels or titles from the axes, the second value is the distance of the tick mark labels from the axes, and the third is the distance of the tick mark symbols from the axes. As with the oma option discussed above, the distances are given in line widths. The defaults for the mgp setting are c(3, 1, 0). The examples below illustrate the effects of changing the various mgp values. Note: the mgp.axis() function in the Hmisc package can be used to change these settings for each axis individually.

Tuesday, October 2, 2012

ImageJ Resources

http://rsbweb.nih.gov/ij/
http://www.fmhs.auckland.ac.nz/sms/biru/facilities/analysis_resources.aspx

Learning ImageJ

ImageJ is a fantastic light-weight tool to analyze and manipulate images. I needed to use it for quickly analyzing microscopy images. Here I will list features of ImageJ that I found particularly useful for my purposes:
- I took a bunch of images at various gains to find out the point where bleaching starts occurring. So I have a series of images in which the pixel intensity varies from 0 to 255.

ImageJ allows me to load the images as a stack and calculate the maximum pixel value in each image by selecting the whole image and hitting 'm' (for measure). Plotting the maximum value gives this:


So, bleaching occurs somewhere between a gain of 450 and 475.

Friday, September 14, 2012

Print page-range using lpr

I use the extremely light-weight pdf viewer, xpdf. For some unknown reason, I cannot print pages from xpdf. A nice workaround I found was with dear old lpr which can print a range of pages thus;
lpr -P HP_LaserJet_6MP file.pdf -o page-ranges=2-5
lpstat -a # Gives the status (and names) of all the connected printers

Wednesday, September 5, 2012

Batch processing images in Gimp

Over the past few weeks I've had to apply a specific set of changes to a large number of images. Doing this repeatedly took a great toll on my soul and Gimp came to my soul's rescue. Take a read at this and this and help yourself.

Thursday, August 23, 2012

Memory convservation in R

Depending on how large a data set you are handling, R can take up large swaths of your RAM and slow down other processes. It is therefore a good idea to remove unused variables.
ls()  # Gives the list of variables/arrays currently in use.
rm(list=ls()) # Removes all the variables and frees up memory.
Useful links:
 http://www.matthewckeller.com/html/memory.html

Wednesday, August 22, 2012

Benchmarking Simulations

It is always a good idea to benchmark your simulations and select the optimal number of cores for your simulations. This exercise greatly reduces wastage of resources and time. The script below helps with the setup. You need files conf.in and template.pbs

for i in 24 48 96 192 240 576 960 1200; do
        mkdir scaling$i
        cp conf.in scaling$i
        sed 's/xxx/'$i'/g' template.pbs > scaling${i}/sub.pbs
        echo "cd scaling$i";
        echo "aprun -n $i $namd conf.in 2>&1 1> conf.out &";  
        echo "cd \$PBS_O_WORKDIR";
done

exit;



----- Template.pbs ------
#PBS -q debug
#PBS -l mppwidth=xxx
#PBS -l walltime=00:30:00
#PBS -N scaling
#PBS -S /bin/bash
#PBS -j oe

namd=/usr/common/usg/namd/2.8/bin/namd2
cd $PBS_O_WORKDIR
aprun -n xxx $namd conf.in 2>&1 1> conf.out

Tuesday, August 21, 2012

Making 2D heat-maps of protein secondary structure

I needed to make 2D heat-maps of protein structure with time on x-axis and protein residues on y-axis. This helps to see the time evolution of structure quite nicely. This is easily accomplished by loading the trajectory in VMD and sourcing the file ss_traj.tcl and going through your entire trajectory once. This creates a buffer with all the structure information. ss_traj.tcl creates a ss_traj.dat file which has the structure information. This ss_traj.dat file is then used by ss_plot.c, after compilation of course, to generate a .ps file with the desired output. All this is explained quite well here. I made a personal copy of the files here:
ss_traj.tcl
ss_plot.c
Sample ss_traj.dat file.

Once you have the output in .ps format you can do interesting things to change the file. The 7th line has the scaling information. The width and height of the output were not to my satisfaction; so I changed the scaling factors to adjust the display. Also the executable could crash when running due to memory requirements. Simply change the dimensions of the array in ss_plot.c according to your needs.

Thursday, August 2, 2012

Reading/processing multiple files in R

j<-1;
for (i in seq(300,390,15)) {
df<-read.table(paste("sasa",i,".txt",sep=``));
# Files are named "sasa300.txt" for ex.
tab[j,]<-cbind(i,mean(df[,2]),sd(df[,2]));
print(tab[j,]);
j<-j+1;
}
> tab
     [,1]     [,2]      [,3]
[1,]  300 3408.514  96.48097
[2,]  315 3422.388 119.14861
[3,]  330 3391.590  81.57252
[4,]  345 3424.176  84.84211
[5,]  360 3394.205 100.37193
[6,]  375 3462.469 122.60486
[7,]  390 3438.328  92.70519


Wednesday, July 25, 2012

Quick and dirty way to plot error bars in R

If you have data that looks as follows, a one line command can draw error bars to the plot.
-x---T-----y-------------error-----
p5 315 2.513402 0.5711628                                                      
p5 330 2.173868 0.4711594                                                      
p5 345 2.132954 0.634045                                                       
p5 360 2.092686 0.4851832                                                      
p5 375 2.966971 0.9165328                                                      
p5 390 2.214886 0.4288291

r<-read.table("data.txt")
plot(r[,2],r[,3],ylim=c(0,4))
lines(r[,2],r[,3])
for(i in 1:length(r[,1])) {segments(r[i,2],r[i,3]+r[i,4],r[i,2],r[i,3]-r[i,4])}

I am drawing a simple line from (x,y+err) to (x,y-err). The result is not as fancy as other efforts but it is enough for my purposes.

Monday, July 23, 2012

Wednesday, July 11, 2012

Adding labels to figures using ImageMagick



This is a 1200x1200 pixel blank file to which I added labels as an exercise in using the annotate flag in ImageMagick's convert.
 
convert blank.gif -pointsize 50 \
-gravity south -append -annotate +000+000 '0s' \
-gravity south -append -annotate +100+100 '1s' \
...

-gravity south -append -annotate +900+900 '9s' \
-gravity north -append -annotate +000+000 '0n' \
-gravity north -append -annotate +100+100 '1n' \
...

-gravity north -append -annotate +900+900 '9n' \
-gravity northwest -append -annotate +000+000 '0nw' \
-gravity northwest -append -annotate +100+100 '1nw' \
...

-gravity northwest -append -annotate +900+900 '9nw' \
-gravity northeast -append -annotate +000+000 '0ne' \
-gravity northeast -append -annotate +100+100 '1ne' \
...

-gravity northeast -append -annotate +900+900 '9ne' \
out.png

Joining images using Latex

Do not forget to use pdflatex (not pdftex) to compile tex files which contain non-eps figures.
 
\documentclass{article}
\usepackage{rotating}
\usepackage{graphicx,subfig}

% Default margins are too wide all the way around. I reset them here
\setlength{\topmargin}{-.5in}
\setlength{\textheight}{9in}
\setlength{\oddsidemargin}{.125in}
\setlength{\textwidth}{6.25in}

\begin{document}


\begin{sidewaysfigure}
\begin{tabular}{cc...c}
\includegraphics[scale=0.10, bb= 0 0 669 834]{view1_mol0} &
\includegraphics[scale=0.10, bb= 0 0 669 834]{view1_mol10} \\

\includegraphics[scale=0.10, bb= 0 0 669 834]{view0_mol0} &
\includegraphics[scale=0.10, bb= 0 0 669 834]{view0_mol10} \\

\includegraphics[scale=0.10, bb= 0 0 669 834]{view2_mol0} &
\includegraphics[scale=0.10, bb= 0 0 669 834]{view2_mol10} \\

\end{tabular}
\end{sidewaysfigure}

\end{document}

Joining images using ImageMagick's convert

convert +append list_of_figures out_1.png
convert +append list_of_figures out_2.png
convert +append list_of_figures out_3.png
convert -append out_1.png out_2.png out_3.png final_out.png

+append puts images side by side while -append adds them top down.
convert -border 2x2 in.png out.png
This puts a light border around images which comes in handy when creating a grid of images from a bunch of individual images which have no border.

Wednesday, July 4, 2012

Empty plots in R

When plotting a grid of graphs in R, I needed leave some cells empty. For this the following commands come handy;
plot(0,xaxt='n',yaxt='n',bty='n',pch='',ylab='',xlab='')
plot.new()
grid.newpage()
grid()

Wednesday, June 20, 2012

Subsetting in R

Following are some example of subsetting in R I have used recently.


> head(crystal)
    V1     V2      V3      V4
1 1ACJ PHE120 290.980 289.101
2 1ACJ PHE153 307.673 283.814
3 1ACJ PHE155 296.153  89.152
4 1ACJ PHE186 311.606 292.186
5 1ACJ PHE187 298.920 270.613
6 1ACJ PHE197  66.678 323.351

>subset(crystal, crystal$V2=="PHE330" & grepl("^2A",crystal$V1))

http://www.ats.ucla.edu/stat/r/faq/subset_R.htm
http://stackoverflow.com/questions/2125231/subsetting-in-r-using-or-condition-with-strings

Monday, June 11, 2012

Charmm2lammps

Charmm2lammps.pl is a useful little code which takes in forcefield [top/par], psf and pdb files in Charmm format and converts them to Lammps data and sample input file. This is extremely useful for running simulations in the much better written MD code, LAMMPS. While trying to simulate a polymer chain I came across a very interesting feature in charmm2lammps; it really expects the force constant in the forcefield parameter file to be non-zero. This works just fine when you never want to specify angle/dihedral parameters to free chains. But when you want to control the parameters in between runs, it is a good idea to define all the angle and dihedrals and then decide to turn them off/on in LAMMPS by setting the force constant to 0/nonzero.

Sunday, June 10, 2012

Compiling C programs on Ubuntu

On Ubuntu, it turns out, this does not work
gcc -lm code.c
but this does
gcc code.c -lm

Thursday, May 10, 2012

Running job on clusters continuously

Here is a way to run jobs on cluster in a continuous fashion. This example addresses NAMD jobs but should also work for others.

Tuesday, May 8, 2012

Labeling figures

http://www.imagemagick.org/Usage/annotating/
This website offers a  nice way to add labels to images that "convert" can handle. I thought it was a nice idea to have my name on figures I generate.

Friday, April 27, 2012

Public folder on Dropbox

http://dl.dropbox.com/u/65895350/

Thursday, April 26, 2012

Extracting coordinates of protein from a simulation

set dir [pwd]
mol new     ${dir}/ache.psf       type {psf}
mol addfile ${dir}/ache.pdb       type {pdb} waitfor all
mol addfile ${dir}/acheminnpt.dcd type {dcd} waitfor all

set molnum 0
set skip 1
set backframe0 [atomselect $molnum backbone frame 0]

for {set i 0} {$i < [molinfo $molnum get numframes]} {incr i $skip} {
set pro  [atomselect $molnum protein  frame $i]

# Change 'protein' to "resid N to Z" to suit your needs.
set back [atomselect $molnum backbone frame $i]
set trans_mat [measure fit $back $backframe0]
$pro move $trans_mat
set k [expr $i/$skip]
$pro writedcd ${dir}/dcd/project-pdb-$k.dcd
}

Now generate a protein-only psf file. At this stage you should have n number of dcd files. To join them all in to one dcd file,

mol new    ${dir}/ache_protein.psf
set pro_frames [expr [molinfo $molnum get numframes]/$skip ]
for {set j 0} {$j < $pro_frames} {incr j 1} {
mol addfile ${dir}/dcd/project-pdb-$j.dcd
}
set top [molinfo top]
animate write dcd {${dir}/dcd/project_protein.dcd} beg 0 end [expr $pro_frames - 1] skip 1 [molinfo top]

The last step is where the individual files are stitched together.

Monday, April 23, 2012

Installing Gimp on Ubuntu 11.1

Last month I installed Gimp on Ubuntu 11.1 which dropped Gimp since they deemed it too complex for new linux converts. Since this was last month I don't remember all the steps I took but I did copy the commands to a file and they might come handy in future. Here they are...

   69  sudo add-apt-repository ppa:matthaeus123/mrw-gimp-svn
   71  sudo apt-get install gimp gimp-data gimp-plugin-registry gimp-data-extras
   73  sudo add-apt-repository ppa:lucid-bleed/ppa
   74  sudo add-apt-repository ppa:matthaeus123/mrw-gimp-svn
   79  mkdir gimp
   80  cd gimp/
   81  wget ftp://ftp.gimp.org/pub/gimp/v2.7/gimp-2.7.2.tar.bz2
   82  tar xjf gimp-2.7.2.tar.bz2
   83  export PATH=/opt/gimp-2.7/bin:$PATH
   84  export PKG_CONFIG_PATH=/opt/gimp-2.7/lib/pkgconfig
   85  export LD_LIBRARY_PATH=/opt/gimp-2.7/lib
   86  cd gimp-2.7.2/
   87  ./configure —prefix=/opt/gimp-2.7
   89  ./configure
   90  cd ..
   92  sudo apt-get install git
   93  git clone git://git.gnome.org/babl
   94  cd gimp-2.7.2/
   95  ./configure --prefix=/opt/gimp-2.7
   96  cd ..
   97  ./autogen.sh --prefix=/opt/gimp-2.7
   99  cd babl/
  100  ./autogen.sh --prefix=/opt/gimp-2.7
  101  make -j5
  102  cd ../gimp-2.7.2/
  103  ./configure --prefix=/opt/gimp-2.7
  104  cd ../babl/
  105  cd ..
  106  git clone git://git.gnome.org/babl
  107  ./autogen.sh --prefix=/opt/gimp-2.7
  108  sudo apt-get install libtool
  109  ./autogen.sh --prefix=/opt/gimp-2.7
  110  cd babl/
  111  ./autogen.sh --prefix=/opt/gimp-2.7
  112  make -j5
  113  sudo make install
  114  cd ../gimp-2.7.2/
  115  ./configure --prefix=/opt/gimp-2.7
  116  cd ..
  117  wget ftp://ftp.gimp.org/pub/gegl/0.1/gegl-0.1.6.tar.bz2
  118  tar -xjf gegl-0.1.6.tar.bz2
  119  sudo apt-get install libjpeg62-dev libopenexr-dev librsvg2-dev
  120  cd gegl-0.1.6/
  121  ./configure --prefix=/opt/gimp-2.7
  122  sudo make install
  123  cd ..
  124  ls
  125  cd gimp-2.7.2/
  126  ./configure --prefix=/opt/gimp-2.7
  127  sudo apt-get install libtiff4-dev python-dev python-gtk2-dev
  128  ./configure --prefix=/opt/gimp-2.7
  129  which gimp
  130  sudo apt-get install libexif-dev liblcms1-dev
  131  ./configure --prefix=/opt/gimp-2.7
  132  make -j5
  133  make install -j5
  134  sudo make install -j5
  135  ls /opt/gimp-2.7/bin/gimp-2.7
  136  /opt/gimp-2.7/bin/gimp-2.7
  137  history > ~/gimpinstallcommands.dat

Making movies with VMD/PyMol


These two scripts help greatly in making and handling movies. I need scripts instead of the GUI because most of my data is on machines on the other coast and it gets rather cumbersome to pull a gigantic trajectory file just to see a quick snapshot of the system. I could make PDB (or better dcd) files of parts of trajectory I am interested in, but I will need to make movies at some point.

view_change_render.tcl
trajectory_movie.tcl
http://www.myofilament.org/documents/howto/modeling/VMD_Tcl.htm

PyMol uses get_view and "set view" commands to save and retrieve views of molecules. VMD handles things a little differently. It needs 4 parameters per view. They are [rotate/center/scale/global]_matrix. Saving and retrieving are done by processes below. They have been taken from view_change_render.tcl
I added the last part get_vp to see what the view point actually looks like (similar to get_view in PyMol).

proc save_vp {view_num} {
  global viewpoints
  if [info exists viewpoints($view_num)] {unset viewpoints($view_num)}
  # get the current matricies
  foreach mol [molinfo list] {
    set viewpoints($view_num,$mol,0) [molinfo $mol get rotate_matrix]
    set viewpoints($view_num,$mol,1) [molinfo $mol get center_matrix]
    set viewpoints($view_num,$mol,2) [molinfo $mol get scale_matrix]
    set viewpoints($view_num,$mol,3) [molinfo $mol get global_matrix]
  }
} 
  
 
 proc retrieve_vp {view_num} {
  global viewpoints
  foreach mol [molinfo list] {
    if [info exists viewpoints($view_num,$mol,0)] {
      molinfo $mol set rotate_matrix   $viewpoints($view_num,$mol,0)
      molinfo $mol set center_matrix   $viewpoints($view_num,$mol,1)
      molinfo $mol set scale_matrix   $viewpoints($view_num,$mol,2)
      molinfo $mol set global_matrix   $viewpoints($view_num,$mol,3)
    } else {
      puts "View $view_num was not saved"}
  }
}
 
 proc get_vp {view_num} {
  global viewpoints
  foreach mol [molinfo list] {
    if [info exists viewpoints($view_num,$mol,0)] {
puts "global viewpoints"
puts "molinfo $mol set rotate_matrix     \"$viewpoints($view_num,$mol,0)\""
puts "molinfo $mol set center_matrix     \"$viewpoints($view_num,$mol,1)\""
puts "molinfo $mol set scale_matrix      \"$viewpoints($view_num,$mol,2)\""
puts "molinfo $mol set global_matrix     \"$viewpoints($view_num,$mol,3)\""
    } else {
      puts "View $view_num was not saved"}
  }
}
 
 
Once you save this output (as a text file) it becomes very easy to retrieve the view even 
after closing down VMD. Simply copy and paste the output of get_vp.

Friday, April 20, 2012

Loops in Tcl/Tk

If loop

if { test1 } {
body1 
} elseif { test2 } {
body2 
} else {
bodyn
}


For loop

for { set i 1 } { $i <= 10 } { incr i } { # This will append all multiples of all numbers for the number n # into a variable called table set table "$table $i x $n = [expr $i \* $n]\n" }
 
 #Make the list
set list [list "Item 1" {Item 2} Last]
set text ""
foreach item $list {
 #Append the every item to $text
 set text "$text\n$item"
}
Foreach loop

#Make the list 
set list [list "Item 1" {Item 2} Last] 
set text "" 

foreach item $list { 
#Append the every item to $text 
 set text "$text\n$item"
 }


Thursday, March 29, 2012

Find non-zero size files in Linux

http://www.unix.com/unix-dummies-questions-answers/25514-how-find-files-not-empty.html

You can use the find command to find non-zero length files:

find path -type f ! -size 0

In most UNIX implementations, the -size expression can also be used to search for file sizes of exactly N bytes (-size Nc), greater-than N bytes (-size +Nc), and less-than N bytes (-size -Nc).

The confusing thing is that the numeric following -size is, by default, 512-byte blocks not a byte count. The numeric must be followed by a 'c' for that. The following command will find files less than 2KB:

find . -type f -size -2048c -print

Conversely, for files greater than 2KB:

find . -type f -size +2048c -print

One note, the 512-byte block count does not directly translate into bytes. It's a long story. You can display a file's block usage with, under Solaris, ls -s. Stick to byte counts.

Oh, yes, one more thing, you can search for a specific range by using multiple -size expressions as long as they can all be satisfied by a single file. For example, locate files larger than 2KB and less than 8KB (inclusive):

find . -type f -size +2047c -size -8193c

Making VMD detect improperly named atoms

mol reanalyze does the job.
More here; http://www.ks.uiuc.edu/Research/vmd/mailing_list/vmd-l/19657.html

Wednesday, March 28, 2012

List of webpages that have come handy

http://ubuntugeeknerd.blogspot.com/2010/01/you-have-not-chosen-to-trust-thawte.html

For a better solution, try this:
sudo ln -s /etc/ssl/certs/Thawte_Premium_Server_CA.pem /usr/lib/ICAClient/keystore/cacerts/

Useful when you get this error;
" Citrix SSL Error 61: You have not chosen to trust “Thawte Server CA”".

Tuesday, March 27, 2012

NAMD sample scripts

http://www.ks.uiuc.edu/Research/namd/2.7/ug/node64.html

This file demonstrates the analysis of a DCD trajectory file using NAMD. The file pair.pdb contains the definition of pair interaction groups; NAMD will compute the interaction energy and force between these groups for each frame in the DCD file. It is assumed that coordinate frames were written every 1000 timesteps. See Sec. 12.1 for more about pair interaction calculations.

# initial config
coordinates     alanin.pdb
temperature     0

# output params
outputname      /tmp/alanin-analyze
binaryoutput    no

# integrator params
timestep        1.0

# force field params
structure       alanin.psf
parameters      alanin.params
exclude         scaled1-4
1-4scaling      1.0
switching       on
switchdist      8.0
cutoff          12.0
pairlistdist    13.5
stepspercycle   20
 
# Atoms in group 1 have a 1 in the B column; group 2 has a 2.
pairInteraction  on
pairInteractionFile pair.pdb
pairInteractionCol B
pairInteractionGroup1 1
pairInteractionGroup2 2

# First frame saved was frame 1000.
set ts 1000

coorfile open dcd /tmp/alanin.dcd

# Read all frames until nonzero is returned.
while { ![coorfile read] } {
  # Set firstTimestep so our energy output has the correct TS.
  firstTimestep $ts
  # Compute energies and forces, but don't try to move the atoms.
  run 0
  incr ts 1000
}
coorfile close

Monday, March 5, 2012

Drawing arrows in Gimp

Gimp (Gnu image manipulation program) is an open source image editor/manipulator that I use regularly to edit images and add text. I often need to add arrows to images and for some strange reason Gimp does not have an arrow button by default. But thanks to
http://registry.gimp.org/node/20269 there is now an easy way to accomplish that. For my purposes, I found these values ideal;
I could have learned a lot by simply reading the asterisk which says that negative values indicate fractions. For example a value of -2 indicates that the length of wings is 1/2 of the length of arrow. A value of -8 for brush thickness indicates that the brush is 1/8th of the length of arrow. For very long arrows one should select very low negative values (-100 or -200) to get reasonable looking arrows.

Wednesday, February 29, 2012

PLINK

PLINK is a free, open-source whole genome association analysis toolset, designed to perform a range of basic, large-scale analyses in a computationally efficient manner.

The focus of PLINK is purely on analysis of genotype/phenotype data, so there is no support for steps prior to this (e.g. study design and planning, generating genotype or CNV calls from raw data). Through integration with gPLINK and Haploview, there is some support for the subsequent visualization, annotation and storage of results.

PLINK (one syllable) is being developed by Shaun Purcell at the Center for Human Genetic Research (CHGR), Massachusetts General Hospital (MGH), and the Broad Institute of Harvard & MIT, with the support of others.


Basic usage for SNP lookup function
plink --lookup rs1475515
which outputs to the LOG file the following information

Wednesday, February 22, 2012

Bookmarks

My favorite online bookmarking tool is delicious.com. It is a pretty neat, no-nonsense website currently run by Chad Hurley and Steve Chen. I typically assign a tag to a saved link and looking at what other people have saved under that tag can be quite educational. Here's how to do it:
delicious.com/tag/name-of-tag

Monday, February 20, 2012

Solvating molecules with VMD

To perform MD simulations with NAMD with Charmm ff, I typically use Charmm to build the initial psf/pdb of the protein and then use VMD to solvate it. Now VMD does not like any psf file generated by Charmm. It likes to its own version of psf file. For this one has to first read in a pdb file and read out a psf file. For this the following script is helpful:


package require psfgen
topology ./top_all27_prot_na.inp
segment PROT { pdb xp5helixonXaxis.out.pdb }
coordpdb xp5helixonXaxis.out.pdb PROT
guesscoord
writepsf vmd.psf

package require solvate
solvate vmd.psf xp5helixonXaxis.out.pdb  -o solvate  -s WT -t 15

Useful resource:
http://www.ks.uiuc.edu/~villa/dna/

Thursday, February 16, 2012

Fitting Protein Structures in VMD

# This script can be used to first load a reference structure and
# fit the second structure/trajectory to the reference.

mol new reference.pdb

mol new enzfibsol.psf
mol addfile md2.dcd type dcd first 0 last -1 step 1 waitfor all
mol addfile md3.dcd type dcd first 0 last -1 step 1 waitfor all
mol addfile md4.dcd type dcd first 0 last -1 step 1 waitfor all
mol addfile md5.dcd type dcd first 0 last -1 step 1 waitfor all

set backbone [atomselect 0 backbone]

for {set i 0} {$i < [molinfo 1 get numframes]} {incr i 1} {

set bk [atomselect 1 backbone frame $i]
set all [atomselect 1 all frame $i]
$all move [measure fit $bk $backbone]

}

Wednesday, February 15, 2012

Image manipulation in Matlab

a = double(imread('figures_from_microscope/500nm_particles_1200.tif'));
colormap('gray'), imagesc(a);

b = bpass(a,0,5,20);
#    bpass(img,lnoise, lobject, threshold)
colormap('gray'), image(b);

pk = pkfnd(b,25,3);
#     pkfnd(im, th, sz)

fid = fopen('exp.txt', 'w');
fprintf(fid, '%6.2f %12.8f\n', pk);
fclose(fid);

pk= pkfnd(b(200:400,200:400), 30,10);

# Below is a way to display multiple figures
figure(1); colormap('gray'), imagesc(a);
figure(2); colormap('gray'), image(b);
figure(3); colormap('gray'), image(b(200:400,200,400));
figure(4); colormap('gray'), image(a(200:400,200:400));

# This will put dots of 'r'ed on the particles of interest.
plot(pk(:,1),pk(:,2),'r.')
Looking at a small section of an image and checking for accuracy of the image manipulation is necessary. This is important since we make many assumptions on what particles to look at and what to ignore [this is what values in bpass and pkfnd do].

If var is a variable you are using in Matlab, it can be saved into a file using:
save('filename.txt', 'var', '-ascii')

These are the relevant links:
http://physics.georgetown.edu/matlab/tutorial.html
http://www.physics.emory.edu/~weeks/idl/tracking.html
http://www.physics.emory.edu/~weeks/idl/index.html

Friday, February 10, 2012

Getting header names in R and playing with csv files


names(myTable)

a<-read.csv("file.csv", header=T, sep=",")
names(a)
motility<-subset(a, Putative.orf.function=="Motility & Attachment")
write.csv(motolity, file="motility.csv")
 
Edit Feb 15th 2012
grep("Motility", a$Putative.orf.function)
gives the list of rows whose Putative.orf.function column contains the string "Motility".
Using this, one can get the entire row information.
df<-read.csv("file.csv", header=T, sep=",")
names(df)
 > names(df)
 [1] "Strain.Name"           "ID"                    "Location"             
 [4] "PA.ORF"                "Gene"                  "Gene.Abbrev."         
 [7] "Putative.orf.function" "Position.in.ORF"       "Frame"                
[10] "Genome.Position"       "Transposon.Direction"  "Transposon"           
[13] "F.Primer.Name"         "F.Primer.Seq"          "F.Primer.Position"    
[16] "F.Primer.Tm"           "Insert...F"            "R.Primer.Name"        
[19] "R.Primer.Seq"          "R.Primer.Position"     "R.Primer.Tm"          
[22] "R...Insert"            "WT.PCR.Len"            "Confirmed."           
[25] "How.confirmed."        "Notes"                
> df$Strain.Name[grep("Attachment",df$Putative.orf.function)]
  [1] PW10299 PW10300 PW1728  PW1729  PW1730  PW1731  PW1749  PW1750  PW1751 
 [10] PW1752  PW1753  PW1754  PW1755  PW1756  PW1757  PW2791  PW2792  PW2794 
 [19] PW2795  PW2941  PW2942  PW2943  PW2944  PW2945  PW2946  PW2947  PW2948 
...
[118] PW8681  PW8682  PW9465  PW9466  PW9467  PW9468  PW9469  PW9470  PW9471 
[127] PW9472  PW9473  PW9474 

Friday, January 27, 2012

Useful commands in Pymol


load file.pdb
create protein, all and segid PROT
create water, all and resname WAT
create res40, protein and resid 40
# To set display to orthoscopic
cmd.set('''orthoscopic''','''1''',quiet=0)
# To reset to default view
reset
hide everything, all
hide everything, protein
show sticks, protein
show surface, protein
set transparency=0.5
bg_color white
# To save images
ray 1200,1200
save file.png
distance (selection1), (selection2)
distance name = (selection1), (selection1) [,cutoff [,mode] ]
fit (selection), (target-selection)
# Colors everything by chain id
util.cbc

Resources:
http://pymol.sourceforge.net/newman/ref/S1000comref.html
http://www.pymolwiki.org/index.php/TOPTOC
http://www.pymolwiki.org
http://www.pymol.org/support
http://www.pymolwiki.org/images/7/77/PymolRef.pdf
http://people.mbi.ucla.edu/sawaya/tutorials/Graphics/pymol.html

The last link is particularly useful in the post-beginner stage of using Pymol.


 
load xxx.pdb
hide everything, all
create protein, all and not name h*
show sticks, protein
distance resi 22 and name CD and chain A, resi 22 and name CD and chain B
distance resi 22 and name CD and chain B, resi 22 and name CD and chain C
distance resi 22 and name CD and chain C, resi 22 and name CD and chain D
distance resi 22 and name CD and chain D, resi 22 and name CD and chain E
distance resi 28 and name NZ and chain D, resi 23 and name OD1 and chain C
distance resi 28 and name NZ and chain D, resi 23 and name OD2 and chain C
distance resi 28 and name NZ and chain C, resi 23 and name OD1 and chain B
distance resi 28 and name NZ and chain C, resi 23 and name OD2 and chain B
distance resi 28 and name NZ and chain B, resi 23 and name OD1 and chain A
distance resi 28 and name NZ and chain B, resi 23 and name OD2 and chain A
hide labels, all

March 2nd 2012

create protein, all and not resn DT+DG+NAG+HOH+OG6
create rna, all and resn DG+DT
create nag, all and resn NAG
create og6, all and resn OG6
hide everything, all
show cartoon, rna
show lines, rna
create closeprotein, (rna around 10) and not resn DG+DT
show sticks, closeprotein
distance /rna//D/DT`13/O4, /closeprotein//H/ARG`75/NH1
distance /rna//D/DT`13/O4, /closeprotein//H/ARG`75/NH2
distance /rna//D/DG`2/OP2, /closeprotein//H/ARG`77A/NH1
distance /rna//D/DG`2/OP2, /closeprotein//H/ARG`77A/NH2


March 5th, 2012

 # simple example: label residue 22's atoms with their names
label i. 22, name
 
# Label residue #44's alpha carbon with it's residue name, number and B-factor.
label n. CA and i. 44, "(%s, %s, %s") % (resn, resi, b)


This link has a lot of info on labeling. http://pymolwiki.org/index.php/Label

Monday, January 23, 2012

Printers

Here are a few commands to work with printers on Suse Linux.

# To check the status of all printers
lpstat -a
# To check the status of a printer
lpstat -p printer
# To set a default printer
lpoptions -d printer-name
lpq
# To print a file
lp -d printer file
# To remove a print job
lprm -Pprinter job-id


sudo -u pkc  /usr/sbin/cupsenable HP_LaserJet_6MP

Friday, January 20, 2012

To merge pdf files in Mac

Here's a neat little trick to combine pdf files on a Mac
http://macintoshhowto.com/leopard/how-to-merge-pdf-files-with-preview-in-leopard.html

Wednesday, January 18, 2012

VMD script to pick a box within a box


set cellxmin [lindex [lindex [measure minmax $all] 0] 0]
set cellxmax [lindex [lindex [measure minmax $all] 1] 0]
set cellymin [lindex [lindex [measure minmax $all] 0] 1]
set cellymax [lindex [lindex [measure minmax $all] 1] 1]
set cellzmin [lindex [lindex [measure minmax $all] 0] 2]
set cellzmax [lindex [lindex [measure minmax $all] 1] 2]

for {set i 0} {$i < 100} {incr i} {
# This lets you pick a random box of size 10x10x10 in the simulation box
set xmin [expr $cellxmin + ( ($cellxmax-$cellxmin-$boxsize) * rand())]
set ymin [expr $cellymin + ( ($cellymax-$cellymin-$boxsize) * rand())]
set zmin [expr $cellzmin + ( ($cellzmax-$cellzmin-$boxsize) * rand())]
set xmax [expr $xmin + $boxsize]
set ymax [expr $ymin + $boxsize]
set zmax [expr $zmin + $boxsize]

set selection [atomselect top "(x>$xmin and x<$xmax and y>$ymin and y<$ymax and z>$zmin and z<$zmax)"]
# This gives the number of atom in that selection
set n [$selection num];
#This gives the number of non-bonded interactions in the 10x10x10 box selected.
puts $file [expr $n * ($n -1)/2 ]
}

Thursday, January 12, 2012

Useful perl code

#!/usr/bin/perl

$infile  = "./test.pdb";
$outa = "./test.pdb.A";
$outb = "./test.pdb.B";
open (FH,$infile) || die;
open (OUTA, ">$outa") || die;
open (OUTB, ">$outb") || die;

while ($buf = )
{
    $x = substr($buf,16,1);
    if ($x eq 'A') { print OUTA $buf; }
    elsif ($x eq 'B') { print OUTB $buf; }
    else { print OUTA $buf; print OUTB $buf; }
}

close FH;
close OUTA;
close OUTB;


# This code reads in a file and if the 17th column in each line matches A/B, that line is put in OUTA/OUTB.This is useful in separating multiple coordinates for particular residues in 3D coordinate file of a protein. Sometimes studying all possible conformations is important especially if it involves an aromatic ring flip or flips in residues with amine ends.

Thursday, January 5, 2012

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