I don't have v15, but I have a reasonable guess. If you look at the beginning of the Z2RCladder area, I define a function Stack, which accepts NaN (not a number). This acts as a NULL number. V11 allows for it; I don't know if v15 does or not. In any case, the object of Stack is to allow use of cases such as Stack(NaN, vec), which simply returns vec, the non-NaN argument. The built-in function stack in v11 gives an error in this case; it requires both arguments to be arrays of appropriate dimensions. I don't know if this hold true in v15.
This behavior is useful when iterating calculations through a number of values, and want to append the result of the most recent cal to the existing array. By setting the initial value to NaN, the the initial calc (with no preceding calc values to append to) does not need to be treated/programmed as a special case.
If you can find an alternate way to implement Stack, then simply replace my original definition. The revised file attached goes another route.I implemented a second version of the Z2RCladder function, in which I initialize the RC array to (0 0) instead of NaN. This results in an extraneous first row in the output array, which is removed before returning the RC values.
Lou
