Replace rows in a data frame based on criteria

Question

I have the following data frame

   id f1 f2
1  a  1  3
2  b  3  5
3  c  4  7

I would like to replace all rows which have f1>3 with a row (i

Answer 1

Here's another approach (taking into account @DWin's comment)

dfrm <- data.frame(id=letters[1:3], f1=c(1,3,4), f2=c(3,5,7))

dfrm[dfrm$f1>3, -1] <- 0
levels(dfrm$id) <- c(levels(dfrm$id), 'x')
dfrm[,1]<- with(dfrm, replace(id, f1==0, 'x')) ; dfrm

     id f1 f2
  1  a  1  3
  2  b  3  5
  3  x  0  0

Using some more data:

set.seed(007); N <- 12
 f1 <- sample(1:9, N, replace=TRUE)
 f2 <- sample(1:9, N, replace=TRUE)
 dfrm2 <- data.frame(id=letters[1:N], f1=f1, f2=f2)

 dfrm2[dfrm2$f1>3, -1] <- 0
 levels(dfrm2$id) <- c(levels(dfrm2$id), 'x')
 dfrm2[,1]<- with(dfrm2, replace(id, f1==0, 'x')) ; dfrm2
   id f1 f2
1   x  0  0
2   x  0  0
3   c  2  5
4   d  1  1
5   e  3  6
6   x  0  0
7   x  0  0
8   x  0  0
9   i  2  6
10  x  0  0
11  k  2  9
12  l  3  9

I deleted my previous code, because they weren't useful for this question.

Answer 2

Something like this:

 x[x$f1 > 3,] <- data.frame('x', 0, 0)

should do the trick!

---

as per @DWin's comment, this won't work with a factor id column. Using this same technique can work like this though:

levels(x$id) <- c(levels(x$id), 'x')
x[x$f1 > 3,] <- data.frame('x', 0, 0)
droplevels(x$id)