I have 3-d data, where first two columns (x,y) are independent and the third column (z) is dependent upon first two. I want to have a surface plot of the data so that I can see what region in (x,y) space gives low values of z and what region gives high values of z. But I am not able to use a surface plot because the data is not regularly spaced as required for using 'surf'. I have attached the mat-file containing three columns for reference. Is there a good way of solving this problem?