Problem with plot..

[Niklas]

This is a easy question I now, but I can't figure it out.
I have made a plot with the values on the x-axis: 10 20 30 40 50.. and with the corresponding values on the y-axis. I need to mark the value in the plot corresponding to the x-axis value 19,56, with som kind of dot or something. I can't calculate the corresponding value to 19,56 couse I don't have any kind of eqvation. Any suggestions?
/Niklas

 

[IRstuff]

I think you need to use an interpolation or other curve fit to get the y-value.

TTFN