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# numpy.isnan

`numpy.``isnan`(x[, out]) = <ufunc 'isnan'>

  Test element-wise for NaN and return result as a boolean array.

  Parameters : | x : array_like Input array.
  Returns : | y : {ndarray, bool} For scalar input, the result is a new boolean with value True if the input is NaN; otherwise the value is False. For array input, the result is a boolean array of the same dimensions as the input and the values are True if the corresponding element of the input is NaN; otherwise the values are False.

  See also

  `isinf`, `isneginf`, `isposinf`, `isfinite`

  Notes

  Numpy uses the IEEE Standard for Binary Floating-Point for Arithmetic (IEEE 754). This means that Not a Number is not equivalent to infinity.

  Examples

      >>> np.isnan(np.nan)
      True
      >>> np.isnan(np.inf)
      False
      >>> np.isnan([np.log(-1.),1.,np.log(0)])
      array([ True, False, False], dtype=bool)