[Numpy-discussion] fixing diag() for matrices

Alan G Isaac aisaac at american.edu
Fri Jul 28 18:25:39 CDT 2006


The following are from pyGAUSS.  
fwiw,
Alan Isaac

#diag: diagonal of matrix as column vector (2D only!)
def diag(x):
	if not isinstance(x,numpy.matrix):
		x = numpy.asanyarray(x)
		assert(len(x.shape)==2), "For 2-d arrays only."
		return x.diagonal(offset=0,axis1=-2,axis2=-1).reshape((-1,1))
	else:
		return x.diagonal().T

#diagrv: insert v as diagonal of matrix x (2D only!)
def diagrv(x,v,copy=True):
        x = numpy.matrix( x, copy=copy )
        stride = 1 + x.shape[1]
	x.flat[ slice(0,x.size,stride) ] = v
	return x






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