Thanks.. Altenbach. U r absolutely right. it has an error -20049. But I don't understand the problem of duplicate x-value. because that I did is I load the x and y value from the textfile.txt and keep in Global variable. then, I send the x-array and y-array into the Spline interpolant.vi.
This is the same way, that I did with another textfile (which is only 200 dim) and it work. but why this file (1000 dim) is not working. Thank you very much for ur kind help. Nopporn
