mask surface files based on values
Hi, I have an Ascii file with x,y,z values with x,y are lat, long and z is stress. I have created a surface with the z values (.grd file) and would like to mask that surface based on the z value. Something like if z<0.5 replace it with NaN. My objective is to create a map that shows values only greater than a certain value and makes the rest transparent. How could I do this. I tried grdmath but cannot write the if condition (syntax errors).