I am plotting a processing map with 5 strain rates with each corresponds to 5 individual temperatures that have flow stress. From the straight-line fitting between stress and strain rate, I got the strain rate sensitivity (SRS) value for every temperature. Now to create a surface of Z which is SRS only a function of strain rate, not a temperature, and how to make this surface for plotting power dissipation map. I am attaching the literature data of (Ravichandran et.al.) with this question. Please clarify my doubt on the code for surface function creation.