Re: Replace elements in a matrix

*To*: mathgroup at smc.vnet.net*Subject*: [mg116454] Re: Replace elements in a matrix*From*: Peter Breitfeld <phbrf at t-online.de>*Date*: Wed, 16 Feb 2011 04:33:52 -0500 (EST)*References*: <ijdo8r$f7a$1@smc.vnet.net>

kiz_0987 wrote: > I'm new to Mathematica and have a question regarding matrices. I was > sure that this problem must have been answered in the past, but could > not find a solution. > > I want to replace some elements in a matrix (based on value) with > elements from another matrix at the same position. Eg: > a = {{0, 1}, {1, 2}}; > b = {{1, 3}, {2, 5}}; > > I want to replace the elements in "a" which are equal to 1 (say) with > the same position elements in b to give: > c = {{0, 3}, {2, 2}}; > > How can I do this? I started with using Position and ReplacePart but > could not figure out how to get it to work in this case (other cases > are documented, such as replacing with a single value). > > Any help appreciated. Thanks. > Try this: apos=Position[a,1]; bvals=Extract[b,apos]; c=ReplacePart[a,Thread[apos->bvals]] -- _________________________________________________________________ Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de