ISNA-func
This function is used to determine whether a value is a missing value or NANUM (not a number).
int ISNA(double d)
d
Return 1 if the input number is a missing value or NANUM, else 0.
aa = NA(); // Assign aa as a missing value bb = ISNA(aa); // Test if aa is a missing value bb = ; // Should return 1. aa = pi; // Assign aa a real value bb = ISNA(aa); // Test if aa is a missing value bb = ; // Should return 0.
NA