Add new columns using a loop in a data frame

Question

I made thi function in R and everything wroks fine:

test<-function (x){
   ma <-apply(x,2,max)
   mi <-apply(x,2,min)
   x2 <-data.frame(x)
   for (i in 1:length(ma))
     x2[,i] <- ifelse(x2[,i]==ma[i],"max",ifelse(x2[,i]==mi[i],"min","FALSE"))
   print (x2)
    }

What should I do if I would make the same adding the information in a new data frame? How can I add new columns automatically?

Thanks a lot

josliber · Accepted Answer · 2013-12-26 15:28:37Z

1

You can actually do this with the apply function:

test <- function(x) {
  x2 <- apply(x, 2, function(y) {
    ifelse(y==max(y), "max", ifelse(y==min(y), "min", "FALSE"))
  })
  return(as.data.frame(x2))
}

df = data.frame(x = c(2, 1, 3), y = c(1, 2, 3))
test(df)
#       x     y
# 1 FALSE   min
# 2   min FALSE
# 3   max   max

answered Dec 26, 2013 at 15:28

josliber

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2 Comments

alexmulo Over a year ago

In the function you made, is x2 tranformed to a matrix and then with 'as.data.frame' in data frame?

josliber Over a year ago

Yeah, apply returns a matrix, so I converted it back to a data frame.

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