On Jul 3, 2013, at 2:27 PM, JiangZhengyu wrote:
>
>
>
> Dear R experts,
>
> I have two matrices (mat1 & mat2) with the same dimension & the cells (row
> and column) are corresponding to each other.
>
> I want to change cell values to NA given values of the corresponding cells in
> mat1 and mat2 are both <1.
>
> E.g. both mat1[2,3] and mat2[2,3] are <1, I will put mat1[2,3]=NA, and
> mat2[2,3]=NA; if either mat1[2,3]>=1 or mat2[2,3]>=1, I will save both cells.
>
> I tried the code, but not working. Could anyone can help fix the problem?
>
> mat1[mat1<1&mat2<1]=NA
> mat2[mat1<1&mat2<1]=NA
I beleive the problem is that after the first NA assignment that mat1 will have
changed. You need to record the status of both mat1 and mat2 before the change:
> both <- mat1<1&mat2<1
> both
[,1] [,2] [,3] [,4]
[1,] FALSE FALSE TRUE TRUE
[2,] TRUE FALSE TRUE TRUE
[3,] FALSE TRUE FALSE TRUE
>
> mat1[both] <- NA
> mat2[both] <- NA
> mat1
[,1] [,2] [,3] [,4]
[1,] 1.5599872 2.209537 NA NA
[2,] NA -1.144140 NA NA
[3,] -0.8516326 NA 1.000368 NA
> mat2
[,1] [,2] [,3] [,4]
[1,] 0.8863107 -0.3863741 NA NA
[2,] NA 1.3185811 NA NA
[3,] 1.4487338 NA 1.051689 NA
There is also formalism:
is.na(object) <- logical.vector so it could have been:
is.na(mat1) <- both
is.na(mat2) <- both
>
>
>> mat1=matrix(rnorm(12),3)
>> mat2=matrix(rnorm(12),3)
>> mat1
> [,1] [,2] [,3] [,4]
> [1,] -1.3387075 -0.7142333 -0.5614211 0.1846955
> [2,] -0.7936087 -0.2215797 -0.3686067 0.7328731
> [3,] 0.6505082 0.1826019 1.5577883 -1.5580384
>> mat2
> [,1] [,2] [,3] [,4]
> [1,] 0.4331573 -1.8086826 -1.7688123 -1.4278934
> [2,] -0.1841451 0.1738648 -1.1086942 1.3065109
> [3,] -1.0827245 -0.4143808 -0.6889405 0.4046203
>
>
> [[alternative HTML version deleted]]
>
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David Winsemius
Alameda, CA, USA
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