Re: [Gnuplot-info] Negative logscale axis

[Tue B. <al...@gm...>]

Thank you very much for the fast and helpfull reply!

The trick was to use the two in conjunction and then manually set a minus
sign on the axis with set format.

Below is the working code:


#!/usr/bin/python
from numpy import *
import Gnuplot, Gnuplot.funcutils
import os, sys, string
import glob
import struct as st
import math
import time


for datafile in glob.glob('*.txt' ):
    f = open(datafile, 'r')
    data = map(string.split, f.readlines())
    g = Gnuplot.Gnuplot(debug=1)
    g.title('Plot of generation ') # (optional)
    g('set xrange[1:102]')
    g('set yrange [0.01:10] reverse')
    g('set format y "-%.3f"')
    g('set logscale xy')
    g('set terminal gif')
    g('set output "'+str(datafile[:-4])+'.gif"')
    g('y(r)=r0+z/r')
    g('r0=0')
    g('z=1')
    g('fit [10:100] y(x) "'+str(datafile)+'" using 1:(-$2) via r0,z')
    g('plot "'+str(datafile)+'" using 1:(-$2), y(x)')


2011/5/19 Hans-Bernhard Bröker <HBB...@t-...>

> On 19.05.2011 13:04, alyflex wrote:
>
>  Hi, I got some data that I want to plot on a double logarithmic scale, but
>> since all the y values are negative, I need a negative logarithmic scale,
>> but I have thus far been unable to make one. Does anyone know how to do
>> this?
>>
>
> Negate the data on creation or on-the-fly (".. using 1:(-$2) .."), and
> revert the y axis ("set yrange reverse").
>
>