Error introduced in builtin function "simpne()"

[rbrownrigg]

An ncl-talk user on 12/9/2019 reported a problem using in which they would get this error message:

fatal:simpne: Must have three or more non-missing values.

When in fact their data had no missing values in the x variable. Indeed, this same message results when running the 1st two 1D examples in the documentation page for simpne().

That error message originates in .../ncl/ni/src/lib/nfp/simpsonW.c. The git log shows that back in 2016, an explicit test for more than 3 non-missing vals was added. At around lines 427-428 (at time of writing), there's this:

nvalid = size_leftmost - nmiss;
if(nvalid < 3) {

Following the code logic, if the x input array is 1D, "size_leftmost" will always be 1, and thus "nvalid" always < 3. I'm not certain about an ND input array and I don't really understand the computation of size_leftmost for the ND case. However, I think the calculation for "nvalid" should be something like:

nvalid = npts - nmiss