Problem with SetFormula from a user defined function

the expression in SetFormula returns values to be inserted in the named wave, not a wave.

If you need to recalculate all of the new values for the wave in one, you can set up a 'dummy' dependency to achieve that.

make some other wave or variable dependent upon a function in which you reset the wave pz.

function func1(wave w, variable v)
    w = v * x
    return 1
end
 
•variable/G var1
•make/N=5 foo
•variable/G vDummy
•vDummy := func1(foo, var1) 
•var1=3
•print foo
  foo[0]= {0,3,6,9,12}

In this code, the dummy variable vDummy is explicitly dependent upon wave foo and variable var1, and the wave foo is effectively dependent upon variable var1.

I think that reentry is somehow blocked so that func1 is executed only once when var1 is changed, otherwise we might do something like:

function func1(string s, variable v)
    wave w = $s 
    w = v * x
    return 1
end
 
vDummy := func1("foo", var1) 

I recommend that you try first to set up the dependency from the commandline using the := syntax to check how things work.

I would suggest to avoid dependency formulas. Nowadays you can nearly always achieve your goal without dependencies, the latter are really hard to debug.

Thanks for the quick replies!

I now used dummy variables that are dependent on a user function which update the desired waves in the course of the function. This works very well for my use-case. 
Thank you Tony for the tips, it really helped!

But I see the point of Thomas, I was also kind of lost in the debugging process with dependencies.