My apologies, because I sent the message before finishing it. i am very
sorry about this. Please find below my message (I use to write the messages
from the end to the beginning... sorry :)).
Dear all,
I am trying to compare two matrices, in order to find in which rows of a
matrix A I can find the same values as in matrix B. I am trying to do it
for matrices with around 2500 elements, but please find below a toy example:
A = matrix(1:10,nrow=5)
B = A[-c(1,2,3),];
So
> A
[,1] [,2]
[1,] 1 6
[2,] 2 7
[3,] 3 8
[4,] 4 9
[5,] 5 10
and
> B
[,1] [,2]
[1,] 4 9
[2,] 5 10
I would like to compare A and B in order to find in which rows of A I can
find the rows of B. Something similar to %in% with one dimensional arrays.
In the example above, the answer should be 4 and 5.
I did a function to do it (see it below), it gives me the correct answer
for this toy example, but the excess of for-loops makes it extremely slow
for larger matrices. I was wondering if there is a better way to do this
kind of comparison. Any idea? Sorry if it is a stupid question.
matbinmata<-function(B,A){
res<-c();
rowsB = length(B[,1]);
rowsA = length(A[,1]);
colsB = length(B[1,]);
colsA = length(A[1,]);
for (i in 1:rowsB){
for (j in 1:colsB){
for (k in 1:rowsA){
for (l in 1:colsA){
if(A[k,l]==B[i,j]){res<-c(res,k);}
}
}
}
}
return(unique(sort(res)));
}
Best,
Charles
On Fri, Oct 31, 2014 at 2:12 PM, Charles Novaes de Santana <
charles.sant...@gmail.com> wrote:
> A = matrix(1:10,nrow=5)
> B = A[-c(1,2,3),];
>
> So
> > A
> [,1] [,2]
> [1,] 1 6
> [2,] 2 7
> [3,] 3 8
> [4,] 4 9
> [5,] 5 10
>
> and
> > B
> [,1] [,2]
> [1,] 4 9
> [2,] 5 10
>
> I would like to compare A and B in order to find in which rows of A I can
> find the rows of B. Something similar to %in% with one dimensional arrays.
> In the example above, the answer should be 4 and 5.
>
> I did a function to do it (see it below), it gives me the correct answer
> for this toy example, but the excess of for-loops makes it extremely slow
> for larger matrices. I was wondering if there is a better way to do this
> kind of comparison. Any idea? Sorry if it is a stupid question.
>
> matbinmata<-function(B,A){
> res<-c();
> rowsB = length(B[,1]);
> rowsA = length(A[,1]);
> colsB = length(B[1,]);
> colsA = length(A[1,]);
> for (i in 1:rowsB){
> for (j in 1:colsB){
> for (k in 1:rowsA){
> for (l in 1:colsA){
> if(A[k,l]==B[i,j]){res<-c(res,k);}
> }
> }
> }
> }
> return(unique(sort(res)));
> }
>
>
> Best,
>
> Charles
>
>
> --
> Um axé! :)
>
> --
> Charles Novaes de Santana, PhD
> http://www.imedea.uib-csic.es/~charles
>
--
Um axé! :)
--
Charles Novaes de Santana, PhD
http://www.imedea.uib-csic.es/~charles
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