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multiply each row in a matrix with the help of the for loop

3 messages · Haris Rhrlp, arun, Dimitris Rizopoulos

arun
# 
HI,

May be this helps:
list1<-lapply(lapply(1:3,function(i) {aa[1:i,,i]<-a[1:i,]*-1
?return(aa[,,i])}),function(x) apply(x,2,function(i) ifelse(i==0,1,x)))
res<-array(unlist(list1),dim=c(nrow(list1[[1]]),ncol(list1[[1]]),length(list1)))


?res
#, , 1
#
?# ?? [,1] [,2] [,3]
#[1,]?? -1?? -1?? -1
#[2,]??? 1??? 1??? 1
#[3,]??? 1??? 1??? 1

#, , 2
#
#???? [,1] [,2] [,3]
#[1,]?? -1?? -1?? -1
#[2,]?? -1?? -1?? -1
#[3,]??? 1??? 1??? 1
#
#, , 3

? # ? [,1] [,2] [,3]
#[1,]?? -1?? -1?? -1
#[2,]?? -1?? -1?? -1
#[3,]?? -1?? -1?? -1


A.K.

----- Original Message -----
From: Haris Rhrlp <haris_r_help at yahoo.com>
To: "R-help at r-project.org" <R-help at r-project.org>
Cc: 
Sent: Tuesday, November 13, 2012 7:41 AM
Subject: [R] multiply each row in a matrix with the help of the for loop

Dear R users,

I have this program
aa<-array(rep(0,27),dim=c(3,3,3))
a<-matrix(rep(1,9),ncol=3)
n<-0

for (i in 1:3) {
? ??
? ? ? a[i,]<-a[i,]*(-1)
? ? ? n<-n+1
? ? ? aa[,,n]<-a[i,]

}

but i real want to multiply each row ?with -1 according to for loop and after that to put it in the array.?

I will give an example for what excaclty want

-1 -1 -1
?1 ?1 ?1
?1 ?1 ?1

-1 -1 -1
-1 -1 -1
?1 ?1 ?1

-1 -1 -1
-1 -1 -1
-1 -1 -1
??? [[alternative HTML version deleted]]


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and provide commented, minimal, self-contained, reproducible code.
Dimitris Rizopoulos
# 
Another alternative is:

aa <- array(0, dim = c(3,3,3))
a <- matrix(1, 3, )

for (i in 1:3) {
      a[i, ] <- -a[i, ]
      aa[, , i] <- a
}

aa

I hope it helps.

Best,
Dimitris