Mathematica 9 is now available
Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2010

[Date Index] [Thread Index] [Author Index]

Search the Archive

Constructing matrix out of submatrices

  • To: mathgroup at smc.vnet.net
  • Subject: [mg113776] Constructing matrix out of submatrices
  • From: Sebastian Schmitt <sschmitt at physi.uni-heidelberg.de>
  • Date: Fri, 12 Nov 2010 05:26:54 -0500 (EST)

Hi!

I would like to construct a matrix out of submatrices. I guess this is
straight forward but somehow I couldn't find the correct way in the
documentation. The example that follows is of course simplified. Please
don't take shortcuts.

I start with a zero matrix and a submatrix:

matrix = ConstantArray[0, {3, 3}]
submatrix = {{a, b}, {c, d}}

I want to specificy the upper-left corner in the matrix where the
submatrix should be placed. If the position is {1,1} the result should be:

result = {{a, b, 0}, {c, d, 0}, {0, 0, 0}}

If it is {1,2}:

result = {{0, a, b}, {0, c, d}, {0, 0, 0}}

etc.

ReplacePart together with ArrayFlatten comes close, but the submatrix
does not "override" zeros:

ReplacePart[matrix, {1, 1} -> submatrix] // ArrayFlatten

{{a, b, 0, 0}, {c, d, 0, 0}, {0, 0, 0, 0}, {0, 0, 0, 0}}

What are possible solutions?

Thanks,

Sebastian


  • Prev by Date: Re: Factor, Extension
  • Next by Date: Re: Balance point of a solid
  • Previous by thread: Re: 2-D Butterworth lowpass filter?
  • Next by thread: Re: Constructing matrix out of submatrices