Columns plotting in gnuplot in same file

Question

I have a file which have 18 columns. Using gnuplot, I want to plot them in this way: 1:2, 3:4, 5:6, ..., 17:18.

I have been trying with a do loop, but I don't know how to include the running index in the loop in the number of the colums. I tried something like that:

for [i=1:18] plot "numbers.dat" using (2*(i-1)+1):(2*(i-1)+2)

Thanks

Answer 1

To have the result of an arithmetical expression used as column index, use the column function:

plot for [i=1:18] "numbers.dat" using (column(2*(i-1)+1)):(column(2*i))