[R] matrix dimension and for loop

[Uwe Ligges]

sonchawan tamkaew wrote:
> 
> Dear all,
> 
> My questions are that if I have
> 
> > x<-rnorm(50)
> > dim(x)<-c(10,5)
> > y=1:5
> > Z<-matrix(0,NROW(x),NROW(y))
> > for (j in 1:NROW(y)) Z[,j]<-x[,j]*y[j]
> 
> 1. Is there any other way to write this without 'for'
> loop?
> 
> 2. and if I don't know the dimension of x, which could
> be only 1 column, how could I write the command
> without using if (NCOL(x)==1), or something like that?
> (in case I want to include them in my function.
> 
> Example of x is a vector.
> > x<-rnorm(10)
> > y=2
> > Z<-matrix(0,NROW(x),NROW(y))
> > for (j in 1:NROW(y)) Z[,j]<-x[,j]*y[j]
> Error in x[, j] : incorrect number of dimensions
> 
> Could anyone please help me to solve these problem?
> Thank you very much for your kindness.


 x %*% diag(y, ncol(x))

Uwe Ligges
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