Hi. I'm making a random dataset and interpolating a surface with tri_surf. When I use regular griding (don't include an X and Y in the statement) the range is 0 to 1 (because I'm using RANDOMU), which is what i want it to be. However, when I add irregular griding, via a pair of RANDOMU arrays to make my X and Y grid, the Z value shoots up to a range of 0 to 10 or 15...it changes every time I run the program. Any ideas on how to get a 0 to 1 range in Z and use irregular griding? here is the code now: x=RandomU(seed,100) y=RandomU(seed,100) z=RandomU(seed,100) z = tri_surf(z,x,y,Nx=240,Ny=240) Thanks for any input. -Nick