R - How to add Column to dataframe with a variable for column title

Question

I try to program a script in R, which should go through a dataframe looking for columns with formal/nominal entries. Finding such a column it should extract all entered values in a vector and add for each of those a column with binary data(0,1).

Problem: sign names to column with a variable data$lev[z] <- data[,x]==lev[z] is not working. lev[] is a vector with names, z is an index for a loop.

Would be great if someone could help me out.

Thanks in advance. Cheers

Answer 1

I believe your only issue is that your last line should have sample[,lev[z]] rather than sample$lev[z] . As you currently have it (ie sample$lev[z] ) you are telling R to assign a vector (TRUE, FALSE, FALSE) to the lev column of sample in row z . In this example, you are trying to put 3 things into one place. Hence your warning message: number of items to replace is not a multiple of replacement length .

A working code would be:

letter <- c("a","b","c")
id <- c(1,2,3)
sample <- data.frame(id,letter)
y <- NCOL(sample)
x <- 0
while ( x < y){ 
  x <- x+1
  test01 <- is.factor(sample[,x])
  if(test01 == TRUE ){ 
    lev <- levels(sample[,x])
    q <- length(lev)
    z <- 0
    while (z < q){ 
      z <- z+1
      sample[,lev[z]] <- sample[,x]==lev[z]
    } 
  } 
}