gnu plot

OutlineBasics

Gnuplot

Kashyap Garimella

modified for CS2810 bySubhashini V

February 28, 2011

Kashyap Garimella Gnuplot

OutlineBasics

IntroductionBasic commands

What can I do ?

I First of all we need to understand what we can do

I Drawing 2D plots

I Drawing 3D plots

I Polar coordinates

I Parametric functions

I Plotting Numeric data

I Other Miscellaneous Stuff


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Limitations

I Floating point exceptions

I Precision in time format

I Problems with 3D like rendering, etc

I ....


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Entering, getting help

I Entering gnuplot - type ”gnuplot” in terminal

I To get help on any topic, you can type ”help < topic >”


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Plotting functions

I Any mathematical expression accepted by C, FORTRAN,Pascal, or BASIC may be plotted. The precedence ofoperators is determined by the specifications of the Cprogramming language.

I help plot; help splot; help replot;

I plot - 2D, splot - 3D

I plot < function >


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Plotting functions addons

I help set; help reset;

I set options; set is used to set various options

I eg:

I set xrange [1,2];

I variables/parameters - a=1; b=a+1;

I eg:

I a=1; b=2; f(x)=ax+b; plot f(x);


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set term

I help set term; read about png, ps, pdf

I eg:

I plot sin(x) with points pointtype 2;

I plot sin(x) with linepoints;

I other options - lines, dots, impulses, etc.


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Plotting data

I help plot datafile;

I help splot datafile;

I Data can taken from file or from stdin

I Data files should have the data arranged in columns ofnumbers. Columns should be separated by white space (tabsor spaces) only, (no commas). Lines beginning with a #character are treated as comments and are ignored byGnuplot.


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Plotting data contd.

I eg:

I plot ”force.dat” using 1:2 title ’Column’, ”force.dat” using 1:3title ’Beam’

I plot ”-” using 1:2 notitle with impulses; # data from stdin

I splot ”force.dat” using 1:2:3 with lines

I set datafile commentschars ”#


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tics, grid, scripts etc

I The xtics command is enormously versatile and there areconvenient options for creating tic marks at regularincrements (regular multiples, in logarithmic scale), andspecial formats for time-related data.

I help xtics

I help mxtics

I gnuplot scripts. Eg: myscript.gnu; Run it by executing”gnuplot myscript.gnu”

I pause -1 # Wait until a carriage return is hit

I pause 3 # Wait three seconds

I pause -1 ”Hit return to continue”

I pause 10 ”Isn’t this pretty? It’s a cubic-spline.”


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Example 1 Bargraphs

I bargraph.gnu


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Curve fitting

I help fit

I example:

I f 1(x) = a1 ∗ tanh(x/b1) # define the function to be fit

I a1 = 300; b1 = 0.005; # initial guess for a1 and b1

I fit f1(x) ’force.dat’ using 1:2 via a1, b1


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Example 2 Curve fitting

I fitting.gnu


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Calling gnuplot from within a python script

I runtest.pl


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