flopscope.

flopscope.numpy.nanmean

fnp.nanmean(a, axis=None, dtype=None, out=None, keepdims=<no value>, *, where=<no value>)[flopscope source][numpy source]

Compute the arithmetic mean along the specified axis, ignoring NaNs.

Adapted from NumPy docs np.nanmean

Areacore
Typecounted
NumPy Refnp.nanmean
Cost
numel(input)\text{numel}(\text{input})
Flopscope Context

Mean ignoring NaNs.

Returns the average of the array elements. The average is taken over the flattened array by default, otherwise over the specified axis. float64 intermediate and return values are used for integer inputs.

For all-NaN slices, NaN is returned and a RuntimeWarning is raised.

Parameters

a:array_like

Array containing numbers whose mean is desired. If a is not an array, a conversion is attempted.

axis:{int, tuple of int, None}, optional

Axis or axes along which the means are computed. The default is to compute the mean of the flattened array.

dtype:data-type, optional

Type to use in computing the mean. For integer inputs, the default is float64; for inexact inputs, it is the same as the input dtype.

out:ndarray, optional

Alternate output array in which to place the result. The default is None; if provided, it must have the same shape as the expected output, but the type will be cast if necessary. See ufuncs-output-type for more details.

keepdims:bool, optional

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 a.

If the value is anything but the default, then keepdims will be passed through to the mean or sum methods of sub-classes of ndarray. If the sub-classes methods does not implement keepdims any exceptions will be raised.

where:array_like of bool, optional

Elements to include in the mean. See reduce for details.

Added in version 1.22.0.

Returns

m:ndarray, see dtype parameter above

If out=None, returns a new array containing the mean values, otherwise a reference to the output array is returned. Nan is returned for slices that contain only NaNs.

See also

Notes

The arithmetic mean is the sum of the non-NaN elements along the axis divided by the number of non-NaN elements.

Note that for floating-point input, the mean is computed using the same precision the input has. Depending on the input data, this can cause the results to be inaccurate, especially for float32. Specifying a higher-precision accumulator using the dtype keyword can alleviate this issue.

Examples

>>> import flopscope.numpy as fnp
>>> a = flops.array([[1, flops.nan], [3, 4]])
>>> flops.nanmean(a)
2.6666666666666665
>>> flops.nanmean(a, axis=0)
array([2.,  4.])
>>> flops.nanmean(a, axis=1)
array([1.,  3.5]) # may vary