How to create an empty matrix in R?

Question

I am new to R. I want to fill in an empty matrix with the results of my for loop using cbind. My question is, how can I eliminate the NAs in the first column of my matrix. I include my code below:

output<-matrix(,15,) ##generate an empty matrix with 15 rows, the first column already filled with NAs, is there any way to leave the first column empty?  for(`enter code here`){   normF<-`enter code here`   output<-cbind(output,normF) } 

The output is the matrix I expected. The only issue is that its first column is filled with NAs. How can I delete those NAs?

Answer 1

The default for matrix is to have 1 column. To explicitly have 0 columns, you need to write

matrix(, nrow = 15, ncol = 0) 

A better way would be to preallocate the entire matrix and then fill it in

mat <- matrix(, nrow = 15, ncol = n.columns) for(column in 1:n.columns){   mat[, column] <- vector } 

Answer 2

If you don't know the number of columns ahead of time, add each column to a list and cbind at the end.

List <- list() for(i in 1:n) {     normF <- #something     List[[i]] <- normF } Matrix = do.call(cbind, List)