isnan — Test for Not-A-Number


\begin{rail} NaN : 'isnan' '(' ( Scalar \vert Matrix ) ')' ; \end{rail}
isnan tests if the argument is equal to NaN. If the test is true, it returns 1, otherwise it returns 0. If the argument is a matrix, the test is performed element-by-element, returning a matrix the same size as the original. $\Longrightarrow$ This is not an built-in function. This function is normally loaded on start-up from the isnan.r file in the standard rlib directory. Use of the -r option, incorrectly setting the RLAB_LIB_DIR environmental variable, or modifying isnan.r may make this function unavailable.
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