def asum (a, dimension=None,keepdims=0):
"""
An alternative to the Numeric.add.reduce function, which allows one to
(1) collapse over multiple dimensions at once, and/or (2) to retain
all dimensions in the original array (squashing one down to size.
Dimension can equal None (ravel array first), an integer (the
dimension over which to operate), or a sequence (operate over multiple
dimensions). If keepdims=1, the resulting array will have as many
dimensions as the input array.
Usage: asum(a, dimension=None, keepdims=0)
Returns: array summed along 'dimension'(s), same _number_ of dims if keepdims=1
"""
if type(a) == N.ndarray and a.dtype in [N.int_, N.short, N.ubyte]:
a = a.astype(N.float_)
if dimension == None:
s = N.sum(N.ravel(a))
elif type(dimension) in [IntType,FloatType]:
s = N.add.reduce(a, dimension)
if keepdims == 1:
shp = list(a.shape)
shp[dimension] = 1
s = N.reshape(s,shp)
else: # must be a SEQUENCE of dims to sum over
dims = list(dimension)
dims.sort()
dims.reverse()
s = a *1.0
for dim in dims:
s = N.add.reduce(s,dim)
if keepdims == 1:
shp = list(a.shape)
for dim in dims:
shp[dim] = 1
s = N.reshape(s,shp)
return s
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