CODEWITHSUNDEEP
rfor-loopif-statement
Paolo Lorenzini
Paolo Lorenzini

Reputation: 725

if else inside for loop

I came across this post about an ifelse statement inside a for loop:

How to create new variables using loop and ifelse statement

var1 <- c(0,0,1,2)
var2 <- c(2,2,2,0)
var3 <- c(0,0,0,2)
var4 <- c(1,2,2,2)

df<-as.data.frame(cbind(var1,var2,var3,var4))
df

 var1 var2 var3 var4 
   0    2    0    1   
   0    2    0    2   
   1    2    0    2   
   2    0    2    2

Based on the post the output would be:

  var1 var2 var3 var4 new
   0    2    0    1   1
   0    2    0    2   0
   1    2    0    2   1
   2    0    2    2   0

Because if in any element in one row there is 1 the corresponding row in the column (new) will be 1 else it will be 0

I wrote something like this:

for (i in 1:nrow(df)){
  if(mean(df[i,] == 1) == 0){
    df$new[i]<- 0}
  else{
    df$new[i]<- 1    
  }}

However, it is giving this output:

var1 var2 var3 var4 new
 0    2    0    1   1
 0    2    0    2   1
 1    2    0    2   1
 2    0    2    2   1

if I modify the code if(mean(df[i,] == 1) == 0) to if(mean(df[i] == 1) == 0) then it works, but in another cases, if I modify the data frame by including 1 at certain position then if(mean(df[i,] == 1) == 0) is correct and not if(mean(df[i] == 1) == 0).

Can anybody explain this behavior? and how can my loop could be modified to be correct all the times? Any explanation highly appreciated!

Upvotes: 0

Views: 110

Answers (2)

Cole
Cole

Reputation: 11255

A vectorized solution is always better:

df$new <- as.integer(rowSums(df == 1) > 0)

As for your code, I think it works. It's likely that while you were testing, you still had df$new in your dataframe which caused the logic to mess up. I can't reproduce the error.

var1 <- c(0,0,1,2)
var2 <- c(2,2,2,0)
var3 <- c(0,0,0,2)
var4 <- c(1,2,2,2)

df<-as.data.frame(cbind(var1,var2,var3,var4))

df2 <- df
df2
  var1 var2 var3 var4
1    0    2    0    1
2    0    2    0    2
3    1    2    0    2
4    2    0    2    2

df2$new <- as.integer(rowSums(df == 1) > 0)
for (i in 1:nrow(df)){
  if(mean(df[i,] == 1) == 0){
    df2$new[i]<- 0}
  else{
    df2$new[i]<- 1    
  }}

df2

  var1 var2 var3 var4 new
1    0    2    0    1   1
2    0    2    0    2   0
3    1    2    0    2   1
4    2    0    2    2   0

Upvotes: 1

geekzeus
geekzeus

Reputation: 895

Based on the data provided

var1 <- c(0,0,1,2)
var2 <- c(2,2,2,0)
var3 <- c(0,0,0,2)
var4 <- c(1,2,2,2)

df<-as.data.frame(cbind(var1,var2,var3,var4))

get_1 <- apply(df, 1, function(x) any(x %in% c(1)))

vec = c()

for (i in get_1){ 
    if(i == 'TRUE'){
        vec <- c(vec, 1)
    }
    else if(i == 'FALSE'){
        vec <- c(vec, 0)
    }
}

df$new <- vec
df

#OUTPUT

#    var1 var2 var3 var4 new
#     0   2    0    1     1
#     0   2    0    2     0
#     1   2    0    2     1
#     2   0    2    2     0

Upvotes: 1

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