Another approach using in-place replacement and thinking with matrix
operations instead of vector operations:
DF <- matrix( c( 0, 0, 1, 0, 0
, NA, 0, 1, 1, 0
, 0, 1, 0, 0, NA )
, byrow=TRUE
, nrow=3 )
DF2 <- DF
DF2[ , -1 ] <- ifelse( !is.na( DF[ , -ncol( DF ) ] )
& 1 == DF[ , -ncol( DF ) ]
, 1
, DF[ , -1 ]
)
On Thu, 22 Sep 2016, Henrik Bengtsson wrote:
which(df == 1, arr.ind=TRUE) is useful here:
df <- matrix(c(0,NA,0,0,0,1,1,1,0,0,1,0,0,0,NA), nrow=3)
df
[,1] [,2] [,3] [,4] [,5]
[1,] 0 0 1 0 0
[2,] NA 0 1 1 0
[3,] 0 1 0 0 NA
## Identify (row,col) indices for 1:s
idxs <- which(df == 1, arr.ind=TRUE)
idxs
row col
[1,] 3 2
[2,] 1 3
[3,] 2 3
[4,] 2 4
## Drop any in the last column
idxs <- idxs[idxs[,"col"] < ncol(df), , drop=FALSE]
idxs
row col
[1,] 3 2
[2,] 1 3
[3,] 2 3
[4,] 2 4
idxs[,"col"] <- idxs[,"col"] + 1L
idxs
row col
[1,] 3 3
[2,] 1 4
[3,] 2 4
[4,] 2 5
df[idxs] <- 1
df
[,1] [,2] [,3] [,4] [,5]
[1,] 0 0 1 1 0
[2,] NA 0 1 1 1
[3,] 0 1 1 0 NA
/Henrik
On Thu, Sep 22, 2016 at 8:13 PM, Jim Lemon <[email protected]> wrote:
Hi Saba,
Try this:
df<-matrix(c(0,NA,0,0,0,1,1,1,0,0,1,0,0,0,NA),nrow=3)
dimdf<-dim(df)
df1<-df==1
df[cbind(rep(FALSE,dimdf[1]),df1[,-dimdf[2]])]<-1
Jim
On Fri, Sep 23, 2016 at 12:27 PM, Saba Sehrish via R-help
<[email protected]> wrote:
Hi
I have a matrix that contains 1565 rows and 132 columns. All the observations are either "0" or
"1". Now I want to keep all the observations same but just one change, i.e. whenever there is "1",
the very next value in the same row should become "1". Please see below as a sample:
df
0 0 1 0 0
NA 0 1 1 0
0 1 0 0 NA
What I want is:
0 0 1 1 0
NA 0 1 1 1
0 1 1 0 NA
I shall be thankful for the reply.
Saba
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