Rcpp function check if missing value

Question

I\'m converting R based code into Rcpp based code. The head of my function is:

NumericMatrix createMatrixOfLinkRatiosC(NumericMatrix matr, double threshold4C         


        

Answer 1

R has both NaN and NA (which is really a special kind of NaN) for representing missing values. This is important to know because there are many functions that check if a value is NaN-y (NA or NaN):

Some truth tables for functions from the R/C API (note the frustrating lack of consistency)

+---------------------+
| Function | NaN | NA |
+---------------------+
| ISNAN    |  t  | t  |
| R_IsNaN  |  t  | f  |
| ISNA     |  f  | t  |
| R_IsNA   |  f  | t  |
+---------------------+

and Rcpp:

+-------------------------+
| Function     | NaN | NA |
+-------------------------+
| Rcpp::is_na  |  t  | t  |
| Rcpp::is_nan |  t  | f  |
+-------------------------+

and from the R interpreter (note: Rcpp tries to match this, rather than the R/C API):

+---------------------+
| Function | NaN | NA |
+---------------------+
| is.na    |  t  | t  |
| is.nan   |  t  | f  |
+---------------------+

Unfortunately it's a confusing landscape, but this should empower you a bit.