numpy.average的用法

numpy.average

numpy.average(a,axis=None, weights=None, returned=False)[source]

Compute the weighted average along the specified axis.

Parameters:

 

a : array_like

Array containing data to be averaged. If a is not an array, aconversion is attempted.

axis : int, optional

Axis along which to average a. If None, averaging is done overthe flattened array.

weights : array_like, optional

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

returned : bool, optional

Default is False. If True, the tuple (average,sum_of_weights)is returned, otherwise only the average is returned.Ifweights=None, sum_of_weights is equivalent to the number ofelements over which the average is taken.

Returns:

average, [sum_of_weights] : array_type or double

Return the average along the specified axis. When returned is True,return a tuple with the average as the first element and the sumof the weights as the second element. The return type isFloatif a is of integer type, otherwise it is of the same type asa.sum_of_weights is of the same type asaverage.

Raises:

ZeroDivisionError

When all weights along axis are zero. See numpy.ma.average for aversion robust to this type of error.

TypeError

When the length of 1D weights is not the same as the shape ofaalong axis.

See also

mean

ma.average

average for masked arrays – useful if your data contains “missing” values

Examples

>>>

>>> data = range(1,5)>>> data[1, 2, 3, 4]>>> np.average(data)2.5>>> np.average(range(1,11), weights=range(10,0,-1))4.0

>>>

>>> data = np.arange(6).reshape((3,2))>>> dataarray([[0, 1],       [2, 3],       [4, 5]])>>> np.average(data, axis=1, weights=[1./4, 3./4])array([ 0.75,  2.75,  4.75])>>> np.average(data, weights=[1./4, 3./4])Traceback (most recent call last):...TypeError: Axis must be specified when shapes of a and weights differ.From：https://docs.scipy.org/doc/numpy/reference/generated/numpy.average.html