Convert negative values to zero in dataframe in R

Question

I have a dataframe in R that I would like to convert all columns (outside the ids) from negative to zero

id1  id2  var1  var2  var3
-1   -1   0     -33     5
-1   -2   9     -10    -1

I can convert all columns with code line like:

temp[temp < 0] <- 0

But I can't adjust it to only a subset of columns. I've tried:

temp[temp < 0, -c(1,2)] <- 0

But this errors saying non-existent rows not allowed

Answer 1

We can use data.table

setDT(d1)
for(j in grep('^var', names(d1))){
 set(d1, i= which(d1[[j]]<0), j= j, value=0)
}

d1
#    id1 id2 var1 var2 var3
# 1:  -1  -1    0    0    5
# 2:  -1  -2    9    0    0

Answer 2

There might be fancier or more compact ways, but here's a vectorised replacement you can apply to the var columns:

mytable <- read.table(textConnection("
id1  id2  var1  var2  var3
-1   -1   0     -33     5
-1   -2   9     -10    -1"), header = TRUE)

mytable[, grep("^var", names(mytable))] <- 
    apply(mytable[, grep("^var", names(mytable))], 2, function(x) ifelse(x < 0, 0, x))
mytable
##    id1 id2 var1 var2 var3
##  1  -1  -1    0    0    5
##  2  -1  -2    9    0    0

Answer 3

Edit a bit your variant

temp[,-c(1,2)][temp[, -c(1,2)] < 0] <- 0

Answer 4

You can try using replace:

> mydf[-c(1, 2)] <- replace(mydf[-c(1, 2)], mydf[-c(1, 2)] < 0, 0)
> mydf
  id1 id2 var1 var2 var3
1  -1  -1    0    0    5
2  -1  -2    9    0    0