gnuplot: plotting a file with 4 columns all on y-a

问题:

I have a file that contains 4 numbers (min, max, mean, standard derivation) and I would like to plot it with gnuplot.

Sample:

24 31 29.0909 2.57451
12 31 27.2727 5.24129
14 31 26.1818 5.04197
22 31 27.7273 3.13603
22 31 28.1818 2.88627

If I have 4 files with one column, then I can do:

gnuplot "file1.txt" with lines, "file2.txt" with lines, "file3.txt" with lines, "file4.txt" with lines

And it will plot 4 curves. I do not care about the x-axis, it should just be a constant increment.

How could I please plot? I can't seem to find a way to have 4 curves with 1 file with 4 columns, just having a constantly incrementing x value.

Thank you.

回答1:

You can plot different columns of the same file like this:

plot 'file' using 0:1 with lines, '' using 0:2 with lines ...

(... means continuation). A couple of notes on this notation: using specifies which column to plot i.e. column 0 and 1 in the first using statement, the 0th column is a pseudo column that translates to the current line number in the data file. Note that if only one argument is used with using (e.g. using n) it corresponds to saying using 0:n (thanks for pointing that out mgilson).

If your Gnuplot version is recent enough, you would be able to plot all 4 columns with a for-loop:

set key outside
plot for [col=1:4] 'file' using 0:col with lines

Result:

Gnuplot can use column headings for the title if they are in the data file, e.g.:

min max mean std
24 31 29.0909 2.57451
12 31 27.2727 5.24129
14 31 26.1818 5.04197
22 31 27.7273 3.13603
22 31 28.1818 2.88627

and

set key outside
plot for [col=1:4] 'file' using 0:col with lines title columnheader

Results in:

回答2:

Just to add that you can specify the increment in the for loop as third argument. It is useful if you want to plot every nth column.

plot for [col=START:END:INC] 'file' using col with lines

In this case it changes nothing but anyway:

plot for [col=1:4:1] 'file' using col with lines