Re: (Q:) ReplacePart + SubMatrix replacement
- To: mathgroup at smc.vnet.net
- Subject: [mg7066] Re: [mg7033] (Q:) ReplacePart + SubMatrix replacement
- From: Allan Hayes <hay at haystack.demon.co.uk>
- Date: Sat, 3 May 1997 22:04:56 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
Fri, 2 May 1997
"m.r." <schaferk at communique.net>
[mg7033] (Q:) ReplacePart + SubMatrix replacement
> For A,B n-by-n, matrices,
> K non empty subset of CartesianProduct[Range[n],Range[n]]...
> i wish to replace the block A[[K]] with the block B[[K]]
As you comment in your full message (copied below ****) ReplacePart
does not seem to perform as expected.
However:
A = Table[0,{3},{3}]
{{0,0,0},{0,0,0},{0,0,0}}
B = Table[1,{3},{3}]
{{1,1,1},{1,1,1},{1,1,1}}
A[[{1,3},{2,3}]] = B[[{1,3},{2,3}]];
A
{{0,1,1},{0,0,0},{0,1,1}}
Of course, much more is possible using this technique
Allan Hayes
hay at haystack.demon.co.uk
http://haystack.demon.co.uk
*********************************
Begin forwarded message:
>From: "m.r." <schaferk at communique.net>
>To: mathgroup at smc.vnet.net
>Subject: [mg7033] (Q:) ReplacePart + SubMatrix replacement
>Organization: Communique Inc.
greetings:
Mma3.0 has added a form of ReplacePart not found in Mma2.2.2:
?ReplacePart[expr,new,pos,npos]
ReplacePart[expr,new,pos,npos] replaces parts at positions pos
in expr by parts at positions npos in new.
For
A,B n-by-n, matrices,
K non empty subset of CartesianProduct[Range[n],Range[n]]
one can use
ReplacePart[A,B,K,{1,1}]
to replace the block A[[K]] with B[[1,1]]. (no problem)
what i wish ( though perhaps unrealistically) is
for
ReplacePart[A,B,K,K]
to replace the block A[[K]] with the block B[[K]].
am i misreading the above usage message for ReplacePart?
if so, how does one do a simple block replace in "one fell swoop"?
sincerely.
m. r.
email replies to
schaferk at tennessee.nrlssc.navy.mil