# dask.array.nanpercentile

dask.array.nanpercentile(a, q, **kwargs)

  Compute the qth percentile of the data along the specified axis, while ignoring nan values.

  This docstring was copied from numpy.nanpercentile.

  Some inconsistencies with the Dask version may exist.

  Returns the qth percentile(s) of the array elements.

  Parameters:
    a array_like

      Input array or object that can be converted to an array, containing nan values to be ignored.

    q array_like of float

      Percentile or sequence of percentiles to compute, which must be between 0 and 100 inclusive.

    axis{int, tuple of int, None}, optional (Not supported in Dask)

      Axis or axes along which the percentiles are computed. The default is to compute the percentile(s) along a flattened version of the array.

    out ndarray, optional (Not supported in Dask)

      Alternative output array in which to place the result. It must have the same shape and buffer length as the expected output, but the type (of the output) will be cast if necessary.

    overwrite_input bool, optional (Not supported in Dask)

      If True, then allow the input array a to be modified by intermediate calculations, to save memory. In this case, the contents of the input a after this function completes is undefined.

    method str, optional (Not supported in Dask)

      This parameter specifies the method to use for estimating the percentile. There are many different methods, some unique to NumPy. See the notes for explanation. The options sorted by their R type as summarized in the H&F paper [1] are:

      1. ‘inverted_cdf’

      2. ‘averaged_inverted_cdf’

      3. ‘closest_observation’

      4. ‘interpolated_inverted_cdf’

      5. ‘hazen’

      6. ‘weibull’

      7. ‘linear’ (default)

      8. ‘median_unbiased’

      9. ‘normal_unbiased’

      The first three methods are discontinuous. NumPy further defines the following discontinuous variations of the default ‘linear’ (7.) option:

      - ‘lower’

      - ‘higher’,

      - ‘midpoint’

      - ‘nearest’

      Changed in version 1.22.0: This argument was previously called “interpolation” and only offered the “linear” default and last four options.

    keepdims bool, optional (Not supported in Dask)

      If this is set to True, the axes which are reduced are left in the result as dimensions with size one. With this option, the result will broadcast correctly against the original array a.

      If this is anything but the default value it will be passed through (in the special case of an empty array) to the mean function of the underlying array. If the array is a sub-class and mean does not have the kwarg keepdims this will raise a RuntimeError.

    weights array_like, optional (Not supported in Dask)

      An array of weights associated with the values in a. Each value in a contributes to the percentile according to its associated weight. The weights array can either be 1-D (in which case its length must be the size of a along the given axis) or of the same shape as a. If weights=None, then all data in a are assumed to have a weight equal to one. Only method=”inverted_cdf” supports weights.

      Added in version 2.0.0.

    interpolation str, optional (Not supported in Dask)

      Deprecated name for the method keyword argument.

      Deprecated since version 1.22.0.

  Returns:
    percentile scalar or ndarray

      If q is a single percentile and axis=None, then the result is a scalar. If multiple percentiles are given, first axis of the result corresponds to the percentiles. The other axes are the axes that remain after the reduction of a. If the input contains integers or floats smaller than `float64`, the output data-type is `float64`. Otherwise, the output data-type is the same as that of the input. If out is specified, that array is returned instead.

  See also

  `nanmean`
  `nanmedian`

    equivalent to `nanpercentile(..., 50)`

  `percentile`, `median`, `mean`
  `nanquantile`

    equivalent to nanpercentile, except q in range [0, 1].

  Notes

  The behavior of numpy.nanpercentile with percentage q is that of numpy.quantile with argument `q/100` (ignoring nan values). For more information, please see numpy.quantile.

  References

  [1]

  R. J. Hyndman and Y. Fan, “Sample quantiles in statistical packages,” The American Statistician, 50(4), pp. 361-365, 1996

  Examples

      >>> import numpy as np
      >>> a = np.array([[10., 7., 4.], [3., 2., 1.]])
      >>> a[0][1] = np.nan
      >>> a
      array([[10.,  nan,   4.],
            [ 3.,   2.,   1.]])
      >>> np.percentile(a, 50)
      np.float64(nan)
      >>> np.nanpercentile(a, 50)
      3.0
      >>> np.nanpercentile(a, 50, axis=0)
      array([6.5, 2. , 2.5])
      >>> np.nanpercentile(a, 50, axis=1, keepdims=True)
      array([[7.],
             [2.]])
      >>> m = np.nanpercentile(a, 50, axis=0)
      >>> out = np.zeros_like(m)
      >>> np.nanpercentile(a, 50, axis=0, out=out)
      array([6.5, 2. , 2.5])
      >>> m
      array([6.5,  2. ,  2.5])

      >>> b = a.copy()
      >>> np.nanpercentile(b, 50, axis=1, overwrite_input=True)
      array([7., 2.])
      >>> assert not np.all(a==b)