Re^2: PDL::Complex question


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Re^2: PDL::Complex question

by Anno (Deacon)

on Mar 22, 2007 at 13:53 UTC ( [id://606024]=note: print w/replies, xml )

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in reply to Re: PDL::Complex question
in thread PDL::Complex question

One should think so, but it doesn't.

Conventional notation would have the 2x2 matrix left, the column vector to the right, so

print "   result: ", $matrixM x $matrixX_assigned_value;
[download]

but that complains

PDL: Dim mismatch in matmult of [2x2] x [2x1]: 2 != 1
[download]

Swapping the factors

print "should be: ", $matrixB_assigned_value;
print "   result: ", $matrixX_assigned_value x $matrixM;
[download]

prints

should be:
[
 [
  [5 8]
 ]
 [
  [10 -5]
 ]
]
   result:
[
 [
  [5 4]
 ]
 [
  [ 4 -5]
 ]
]
[download]

The result looks like a column vector, but is numerically incorrect.

BTW, it helps to cast the piddles into the PDL::Complex data type, using the cplx function. That overloads stringification so that the complex elements are printed in a x + i*y format instead of looking like pairs of reals. The numeric discrepancy remains, however.

Anno