How to create an empty matrix in R?

r matrix na
user3276582 picture user3276582 · Feb 5, 2014 · Viewed 286.9k times · Source

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

Christopher Louden picture Christopher Louden · Feb 5, 2014

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
}

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