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change cell values

5 messages · Rui Barradas, JiangZhengyu, arun +1 more

Original
Rui Barradas
# 
Hello,

It's not working because you are changing mat1 before the second 
condition is evaluated, and so mat1 is full of NA values. Try the following.



tmp <- mat1  # Make a copy
tmp[mat1 < 1 & mat2 < 1] <- NA  # And change that copy
mat2[mat1 < 1 & mat2 < 1] <- NA
mat1 <- tmp
rm(tmp)


Hope this helps,

Rui Barradas

Em 03-07-2013 22:27, JiangZhengyu escreveu:
arun
# 
Hi,

set.seed(24) 
mat1=matrix(rnorm(12),3)
set.seed(28)
mat2=matrix(rnorm(12),3)
?indx<- mat1<1 & mat2<1
mat1[indx]<-NA
?mat2[indx]<-NA
?mat1
#???? [,1] [,2] [,3]??????? [,4]
#[1,]?? NA?? NA?? NA 0.002311942
#[2,]?? NA?? NA?? NA????????? NA
#[3,]?? NA?? NA?? NA 0.598269113
?mat2
#???? [,1] [,2] [,3]???? [,4]
#[1,]?? NA?? NA?? NA 1.841481
#[2,]?? NA?? NA?? NA?????? NA
#[3,]?? NA?? NA?? NA 1.520367
A.K.

----- Original Message -----
From: JiangZhengyu <zhyjiang2006 at hotmail.com>
To: "r-help at r-project.org" <r-help at r-project.org>
Cc: 
Sent: Wednesday, July 3, 2013 5:27 PM
Subject: [R] change cell values




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
? ? ? ? ?  [,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
? ? ? ? ?  [,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
#
On Jul 3, 2013, at 2:27 PM, JiangZhengyu wrote:

            

      
      
      
    

        
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:

            

      
      
      
    

        
[,1]  [,2]  [,3] [,4]
[1,] FALSE FALSE  TRUE TRUE
[2,]  TRUE FALSE  TRUE TRUE
[3,] FALSE  TRUE FALSE TRUE

            

      
      
      
    

        
[,1]      [,2]     [,3] [,4]
[1,]  1.5599872  2.209537       NA   NA
[2,]         NA -1.144140       NA   NA
[3,] -0.8516326        NA 1.000368   NA

            

      
      
      
    

        
[,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

            

      
      
      
    

        

      
      
    

        
David Winsemius
Alameda, CA, USA