CODEWITHSUNDEEP
rreplacedataframe
Silke
Silke

Reputation: 177

R replace element in data frame

This is the code to implement my data frame: 

breast <- read.table("breastdata.txt", header=T, sep=" ", fill=TRUE)

Now I want like to replace the first column, that contains factor M and B, to the factor -1 and +1. So when it is "M" then I would replace it by +1. I've got the next code but it doesn't work: 

for(i in 1:569)      
{   
  if(breast[i,1]=="M")  
  {   
    breast[i,1] <- as.factor(-1)   
   }   
  else{   
    breast[i,1] <- as.factor(1)   
  }   
}

Could someone help me?

Upvotes: 1

Views: 243

Answers (2)

rischan
rischan

Reputation: 1585

breast$first_column[breast$first_column=="B"] <- "1"
breast$first_column[breast$first_column=="M"] <- "-1"

Upvotes: 2

gagolews
gagolews

Reputation: 13076

Assuming that levels(breast[,1]) == c("B", "M"), just call:

levels(breast[,1]) <- c("1", "-1")

This will only change the factor's labels, without changing its internal representation. Thus, it is a very fast operation.

Upvotes: 2

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