Gnuplot: using data from multiple data files for the same plot line

2
votes

I am trying to generate a gnuplot that uses data from two different data files for the same plot line, something like this:

plot 'datafile1.dat' using 1:($2/('datafile2.dat' using 2)

i.e. x-axis: column 1 from datafile1.dat; y-axis: (column 2 of datafile1.dat) divided by (column 2 of datafile2.dat)

The syntax above is obviously incorrect, but is there a way to achieve this using gnuplot?

An example input data set is as follows: (Both data files have similar set of data)

nSp   Kf  
10    523276.8  
50    6915841.1  
100   24736818.3  
500   622677171.35  
1000  2892599744  
...

Other solutions I have read online required concatenation of datafile1.dat and datafile2.dat before using plot. The actual data files have many more columns that are used for other plots and hence I wish to avoid this concatenation. If anyone has an alternate solution that keeps the two files separate, I would be very grateful.

Thank you!

2
gnuplot
Maybe you give some mock data and an idea of the result you want to have. It is possible to plot from two different files, so the intended result must be clear. - vaettchen
thank you @vaettchen for the edits, I have updated the question with a closer description of what I want. - confused

2 Answers

4
votes

You can merge the two files in a single fictitious file with the paste utility. gnuplot allows to call a command with the "<" syntax:

plot "< paste datafile1.dat datafile2.dat" using 1:($2/$4)

See this example

produced with these two datafiles:

datafile1.dat

1   1
2   2
3   3
4   4
5   5

datafile2.dat

1   3
2   6
3   5
4   4
5   7
2
votes

In version 5.4, you can store the second column of 'data2.txt' into a data block and then use it for plotting.

set table $divider
plot "data2.txt" using 2 with table
unset table

plot "data1.txt" using 1:($2/$divider[$0+1]) with linespoints