[R] row*matrix

smajor semajor at ncsu.edu
Sat Aug 6 22:35:26 CEST 2011


Hi all, I'm learning R. I'm used to Matlab and am having the following issue:

I define a column vector and matrix and then multiply them.  The result is
not what I expect:
v2 <- c(0,1,0)
M <- cbind(c(1,4,7),c(2,5,8),c(3,6,9))
M*v2

     [,1] [,2] [,3]
[1,]    0    0    0
[2,]    4    5    6
[3,]    0    0    0

I expect the result to be a column, specifically the 2nd column of M.

Now I want to left multiply the matrix by a row vector, and I get errors:
t(v2)*M
Error in t(v2) * M : non-conformable arrays
> V2 <- t(v2)
> V2*M
Error in V2 * M : non-conformable arrays
I would expect to get the 2nd row of M as an output.

Why am I not getting a column for the first case?  Why is the second case
causing errors?  Any help would be greatly appreciated.  I can get the 

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