gnuplot: min and max values for arbitrary number of columns

Question

I'm trying to plot an arbitrary number of lines in a same plot. My data file is like the following:

1  10  15  20
2  20  25  30
3  30  35  40
4  40  45  50
5  50  55  60

I'm using multiplot to do this:

set multiplot
do for [i=1:ny] {
       plot 'data.dat' u 1:i+1 with lines lc i title word(names,i)
}
unset multiplot

where ny=3 in this example. As expected, the yrange of each plot is different, so the graph looks very messy. I'm trying to add

set yrange [ymin:ymax]

where ymin=min(col2,col3,col4,...,coln) is the minimum value among all the columns 2-n and ymax is the maximum value. However, I still don't know how to get ymin and ymax. The function stats allow me to get minimums and maximums for one or two columns at the same time, but no more. Even if I do this column by column, I still don't know how to get the maximum among n scalars.

Any idea?

DragonHu · Accepted Answer · 2014-11-11 10:00:06Z

1

You can use if statement, here is the code:

ymin=1000 #set ymin to a very large value
ymax=0    #set ymax to a very small value
do for [i=1:ny] {
stats "data.dat" u i+1
if (STATS_min < ymin) {ymin=STATS_min}
if (STATS_max > ymax) {ymax=STATS_max}
}

edited Nov 11, 2014 at 10:00

answered Nov 11, 2014 at 9:41

DragonHu

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Comments

Christoph · Accepted Answer · 2014-11-11 08:16:57Z

0

Usually, multiplot isn't for drawing multiple plots in one graph, but to draw several beneath each other. I guess you want to iterate inside the plot command:

plot for [i=1:ny] 'data.dat' u 1:i+1 with lines lc i title word(names, i)

This uses ranges which cover the values of all sub-plots. And it gets the key right.

answered Nov 11, 2014 at 8:16

Christoph

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1 Comment

Looper Over a year ago

Thanks! That's what I was actually looking for.

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