CODEWITHSUNDEEP
r
Ashish
Ashish

Reputation: 73

Apply function in data frame

I have a data frame named Cat. I have multiple columns. In one vector named Jan.15_Transaction I have values. I want to apply a condition that if value is greater than 0 then 1 else 0. So I do not want to use if else condition as there are 42 columns similar to this in which I want to apply the same the same logic.

Jan.15_Transaction   Feb.15_Transaction  
1                         1    
2                         2  
3                         3  
4                         4

Hence I build this function

myfunc <- function(x){
if(x > 0){
  x=1
} 
else {
  x=0
}
return(x)
}

This is getting applied to first element only when I use this code.

Cat$Jan.15_Transaction.1<-myfunc(Cat$Jan.15_Transaction)

Warning message: In if (x > 0) { : the condition has length > 1 and only the first element will be used

So I tried sapply and got this error below

sapply(Cat$Jan.15_Transaction.1, myfunction(Cat))

Error in match.fun(FUN) : argument "FUN" is missing, with no default

Upvotes: 1

Views: 414

Answers (2)

Rithwik
Rithwik

Reputation: 11

I am assuming you want to apply the function on columns which have names ending with '_Transaction'. This can be done with the base function grepl.

vars <- grepl('_Transaction', names(df))
df[, vars] <- ifelse(df[, vars] > 0, 1, 0)

You could also use dplyr like shown below. This would generalize to more complicated functions too.

binarizer <- function(x) ifelse(x > 0, 1, 0)

df <- bind_cols(
  df %>% select(-ends_with('_Transaction')),
  df %>% select(ends_with('_Transaction')) %>% 
    mutate_each(funs(binarizer))
)

Upvotes: 1

Konrad Rudolph
Konrad Rudolph

Reputation: 545508

You can use the ifelse function to vectorise (= apply across a vector) an if statement:

myfunc = function (x)
    ifelse(x > 0, 1, 0)

Alternatively, you could use the following which is more efficient (but less readable):

myfunc = function (x)
    as.integer(x > 0)

Coming back to your original function, your way of writing it is very un-R-like. A more R-like implementation would look like this:

myfunc = function (x)
    if (x > 0) 1 else 0

— No need for a temporary variable, assignments, or the return statement.

Upvotes: 2

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