Use Strings as x-axis labels.

[franciscoGPS]

Is there a way to use dates for the x axis labels? I had to display the date in miliseconds but it'd great to use any other format as long as the X and Y arrays contain the same amount of elements.

[christopherzimmerman]

Currently it's not possible since I enforce that it's a number. I don't believe that gnuplot has the same constraint, so it should be an easy fix. A PR would be welcome!