How to plot viscosity in xmgrace by gmx tcaf

GROMACS version: 5.1.5
GROMACS modification:

Hii,

I am facing a problem in plotting viscosity in xmgrace. Actually I am unable to know how to change k value into k^2 in x-axis in xmgrace.

You want to plot as a function of k^2 instead of k?

Data → Transformations → Evaluate expression and enter x=x*x

Thank You, Sir