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scipy.stsci.image.median

scipy.stsci.image.median(arrays, output=None, outtype=None, nlow=0, nhigh=0, badmasks=None)

median() nominally computes the median pixels for a stack of identically shaped images.

arrays specifies a sequence of inputs arrays, which are nominally a

stack of identically shaped images.

output may be used to specify the output array. If none is specified,

either arrays[0] is copied or a new array of type ‘outtype’ is created.

outtype specifies the type of the output array when no ‘output’ is

specified.

nlow specifies the number of pixels to be excluded from median

on the low end of the pixel stack.

nhigh specifies the number of pixels to be excluded from median

on the high end of the pixel stack.

badmasks specifies boolean arrays corresponding to ‘arrays’, where true

indicates that a particular pixel is not to be included in the median calculation.

>>> a = np.arange(4)
>>> a = a.reshape((2,2))
>>> arrays = [a*16, a*4, a*2, a*8]
>>> median(arrays)
array([[ 0,  6],
       [12, 18]])
>>> median(arrays, nhigh=1)
array([[ 0,  4],
       [ 8, 12]])
>>> median(arrays, nlow=1)
array([[ 0,  8],
       [16, 24]])
>>> median(arrays, outtype=np.float32)
array([[  0.,   6.],
       [ 12.,  18.]], dtype=float32)
>>> bm = np.zeros((4,2,2), dtype=np.bool8)
>>> bm[2,...] = 1
>>> median(arrays, badmasks=bm)
array([[ 0,  8],
       [16, 24]])
>>> median(arrays, badmasks=threshhold(arrays, high=25))
array([[ 0,  6],
       [ 8, 12]])