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

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

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