Linux: Compress PDF – Reduce PDF Size

The large size of a PDF file won’t permit to send it by email because of the probable limitation on the maximum size of attachments. In Linux you can compress a PDF file from the command line without losing its quality, with the help of ps2pdf tool, that is a part of ghostscript suite.

From this article you will learn how to compress a PDF file and significantly reduce its size from the Linux command line.

First of all it is required to install the ghostscript suite that provides the ps2pdf utility. To get this open the linux terminal and execute the following command.

sudo apt-get install ghostscript

Compress PDF File In Linux Run the following command to compress and reduce the size of the BIG.pdf file and save the result to the SMALL.pdf file:

ps2pdf BIG.pdf Small.pdf

Results are pretty amazing:

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How to keep chain ID / IDs in GROMACS?

In GROMACS , while converting pdb file (monomer or multimer) into .gro file, it do not preserve the chain ID information. Due to the lack of chain ID information, pdb file retrieved from .gro file at any stage of the simulation has missing chain IDs and pdb file can not be visualized properly in PYMOL / RASMOL . There are two ways to convert .gro file into .pdb Lets say your protein name is xyz.pdb 1] gmx editconf -f xyz.gro -o xyz.pdb 2] gmx trjconv -f xyz.gro -o xyz.pdb -s xyz.tpr Only ' trjconv ' will retrieve the chain ID information for all the chains. and not ' editconf '. If you have monomer protein and wish to assign any chain ID then following command will be of your interest: gmx editconf -f xyz.gro -o xyz.pdb -label [ chain-ID ]

GNUPLOT: How to draw trend line?

How to draw trend line in the GNUPLOT? If you like to plot graphs in gnuplot and dont know how to plot trendline then here you are. Follow the steps mentioned below... 1. You should have a files with X and Y values 2. Open GNUPLOT (Operating system dosen't change anything here. It works on all systems) 3. Type the command in the gnuplot terminal Lets say I have a file for eg. '1.txt' p '1.txt' u 1:2 w d title '', '1.txt' u 1:2 smooth acsplines title '1.txt' OR p '1.txt' u 1:2 w d title '', '1.txt' u 1:2 smooth bezier title '1.txt' It will plot as below...

Python : Turtle tree

Turtle module can be used to draw some very nice patterns in Python. Following are some examples with code. ==================== import turtle import random t = turtle.Turtle( shape = "circle" ) t.lt( 90 ) lv = 14 l = 120 s = 30 t.color( 'indigo' ) t.width(lv) t.penup() t.bk(l) t.pendown() t.fd(l) def draw_tree ( l , level ): width = t.width() # save the current pen width t.width(width * 3.0 / 4.0 ) # narrow the pen width l = 3.0 / 4.0 * l #t.color(R,G,B) #provide the RGB numbers t.color(random.random(), random.random(), random.random()) t.lt(s) t.fd(l) if level < lv: draw_tree(l, level + 1 ) t.color(random.random(), random.random(), random.random()) t.bk(l) t.rt( 2 * s) t.fd(l) if level < lv: draw_tree(l, level + 1 ) t.color(random.random(), random.random(), random.random()) t.bk(l) t.lt(s) t.width(width) # restore the previous pen width t.speed( "fastest" ) draw_tree(l, 5 ) turtle.done() ===========

MD convert (xtc to dcd)

CATDCD program can be used to convert one file format to another file format. For example: How to convert trajectory output of GROMACS .xtc format into NAMD .dcd format ==== /path/to/catdcd -o /path/to/save/file/abc.dcd -xtc /input/path/to/save/file/abc.xtc ==== How to install CATDCD? Follow the link- https://www.ks.uiuc.edu/Development/MDTools/catdcd/ Download the catdcd-X.Xx.tar.gz Extract all files from the tar. Locate the catdcd file. It should be in directory : catdcd-4.0b/LINUXAMD64/bin/catdcd4.0/ Source the catdcd in your bashrc: export PATH="/path/to/catdcd/directory/:$PATH"

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