Using external function SAMPLEXY

[Russell Fiedler <fiedler@xxxxxxxxxxxxxxx>]

Hi all,

I'm having a real problem getting the external function to work in a
useful way. The problem has been reported before but I didn't see an
answer in the mail archives.

I have 4D data set for which I wish to extract a track for several depths
and all times.

I have 2 variables xpos, ypos which are the locations of the points

I define a variable 

let tsamp=samplexy(temp,xpos,ypos)

When I try to list tsamp I find that all the values are bad.

As a test I tried a simple test

let xpos=180
let ypos=0

Result was again all bad.

Then I tried

let xpos=x[gx=temp,x=180]
let ypos=y[gy=temp,y=0]

and got what looked like a reasonable answer.

Now how do I sample a whole collection of points at once without having
to revert to some very strange loop structure?

Russ

PS: I know about the old way of sampling data, I'm trying to get this new
way to work.