Re: Contour plots

[Peter Gawthrop]

Hi Henry,

  the raw gnuplot functions - see:
    http://gnuplot.sourceforge.net/demo/contours.html
  work well for me. My code follows where F3g.dat contains the colums
  for (x,y,f(x,y)) in gnuplot format (ie with spaces to separate the
  jumps in x).
    

  Peter.

#! /bin/sh
gnuplot<<EOF
# Plots cost contour
set nosurface
set contour
set cntrparam levels 30
set nokey
set out "F3_cont.dat"
set term table
splot "F3g.dat"
set term epslatex mono
set out "Figs/$1.eps"
set grid
set xtics 0.5
set xlabel "$\\\\hat{k}/k$"
set ylabel "$\\\\hat{\\\\mu}/\\\\mu$"
set size square 0.75,0.75
plot "F3_cont.dat" with lines
EOF



From: "Henry F. Mollet" <address@hidden>
Subject: Contour plots
Date: Sun, 06 Mar 2005 10:22:13 -0800

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> GNU Octave, version 2.1.46 (powerpc-apple-darwin6.6).
> G N U P L O T
>         Version 3.8i patchlevel 0
> 
> octave:1> help contour
> contour is the user-defined function from the file
> /sw/share/octave/2.1.46/m/plot/contour.m
>  - Function File:  contour (Z, N)
>  - Function File:  contour (X, Y, Z, N)
>      Make a contour plot of the three-dimensional surface described by
>      Z.  Someone needs to improve `gnuplot''s contour routines before
>      this will be very useful.
> 
> Second function file does not work for me to get better control over the
> number of contours. There are additional difficulties when used in
> combination with multiplot.
> 
> See attached for the best I was able to come up with. Of *most concern* is
> the jaggedness of the contours as the parameter w/al increases. It does not
> appear to be related to the meshgrid. 35x35 produces a similar plot as
> 350x350 (see below), and my computer cannot handle 1000x1000 and I have to
> force quit the terminal window.
> How is this problem best defined so that I could search for a solution?
> Additional problems are the placement of the y-scale on the right instead of
> on the left and the horizontal instead of vertical placement of the y-label.
> 
> I could calculate the contours as y = y(x) but that might be a lot of work.
> Well, perhaps easy with fsovle for a good number of x-values for each
> contour (about 10-15 for each subplot) if I were more familiar with it?
> However, I assume that this would really be a work around?
> Henry
> 
> % Code for last of 4 contour subplots:
> % x = Sa/la from 0 to 1.2
> % y = alpha from 1 to 35
> % w = 12* alpha
> subplot (2,2,4)                                        %  subplot (2,2,4)
> gset origin 0.30,-0.07
> axis ([0.2,1.2,0,35], "square"); % problems with "normal"
> gset label 4 " D)  w/al = 12.0 " at 0.25, 27.5
> grid "on"
> x=linspace(0,1.2,350);
> y=linspace(1,35,350);
> [xx,yy]=meshgrid(x,y);
> z=xx./(yy.*(1-xx)) -
> (12*yy-yy+1).*xx.^(12*yy-yy+1)./yy./(1-xx.^(12*yy-yy+1)) + eps;
> xlabel ("Sa/lambda1")
> ylabel (" alpha")
> contour (x,y,z)
> 



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