[R] remove elements from matrix

[Ulrich Staudinger]

Am 30.09.2011 11:30, schrieb Alaios:
> Dear all,
> I have a numeric vector that contains indices.
> I also have two matrices of [1,m] dimension and of [m,n] dimension.
>
> I want for every indexto remove the current element from the [1,m] vector an the row from the [m,n] matrix.
> How I can do that efficiently in R? So to say not have a for loop getting parameter after parameter and then removing row by row from the vector and the matrix.
>
>    

This should get you there ...

 > indexVec = c(2,3)
 > indexVec
[1] 2 3

 > mat1 = matrix(rnorm(4),1,4)
 > mat1
            [,1]        [,2]     [,3]       [,4]
[1,] -0.4535787 -0.09076038 1.156931 -0.9116866
 >

 > mat2 = matrix(rnorm(4),4,1)
 > mat2
            [,1]
[1,] -1.4346468
[2,] -0.1764882
[3,]  0.8840969
[4,] -0.8722242
 >

 > trueFalseIndex = rep(FALSE, length(mat1))
 > trueFalseIndex
[1] FALSE FALSE FALSE FALSE
 > trueFalseIndex[indexVec] = TRUE
 > trueFalseIndex
[1] FALSE  TRUE  TRUE FALSE

 > mat1[!trueFalseIndex]
[1] -0.4535787 -0.9116866
 >


I assume you can make the transfer to filter mat2 yourself ...


Regards,
Ulrich