Calculation between vectors in nested for loops

Question

I am struggling with an issue concerned with nested for loops and calculation with conditions.

Let's say I have a data frame like this:

df = data.frame("a" = c(2, 3, 3, 4), 
                "b" = c(4, 4, 4, 4), 
                "c" = c(5, 5, 4, 4), 
                "d" = c(3, 4, 4, 2))

With this df, I want to compare each element between vectors with a condition: if the absolute difference between two elements is lower than 2 (so difference of 0 and 1), I'd like to accord 1 in a newly created vector while the absolute difference between two elements is >= 2, I'd like to append 0.

For example, for a calculation between the vector "a" and the other vectors "b", "c", "d", I want this result: 0 0 1. The first 0 is accorded based on the difference of 2 between a1 and b1; the second 0 is based on the difference of 3 between a1 and c1; the 1 is based on the difference of a1 and d1. So I tried to make a nested for loop to applicate the same itinerary to the elements in the following rows as well.

So my first trial was like this:

list_all = list(df$a, df$b, df$c, df$d)

v0<-c()

for (i in list_all)
  for (j in list_all)
    if (i != j) {
      if(abs(i-j)<2) { 
        v0<-c(v0, 1) 
      } else { 
        v0<-append(v0, 0)
      }} else { 
        next}

The result is like this :

v0
[1] 0 0 1 0 1 1 0 1 0 1 1 0

But it seems that the calculation has been made only among the first elements but not among the following elements.

So my second trial was like this:

list = list(df$b, df$c, df$d)

v1<-c()

for (i in df$a){
  for (j in list){
    if(abs(i-j)<2) { 
      v1<-append(v1, 1) 
    } else { 
      v1<-append(v1, 0)
    }
  }
}
v1 

v1
[1] 0 0 1 1 0 1 1 0 1 1 1 1

It seems like the calculations were made between all elements of df$a and ONLY the first elements of the others. So this is not what I needed, either.

When I put df$b instead of list in the nested for loop, the result is even more messy.

v2<-c()

for (i in df$a){
  for (j in df$b){
    if(abs(i-j)<2) { 
      v2<-append(v2, 1) 
    } else { 
      v2<-append(v2, 0)
    }
  }
}
v2     
 [1] 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1

It seems like the calculation has not been made between the corresponding elements (in the same rows), but between all vectors regardless of the place.

Could anyone tell me how to fix the problem? I don't understand why the nested for loop works only for the first elements.

Thank you in advance.

Answer 1

I'm not sure if I understood it all correctly, but how about this?

df = data.frame("a" = c(2, 3, 3, 4), 
                "b" = c(4, 4, 4, 4), 
                "c" = c(5, 5, 4, 4), 
                "d" = c(3, 4, 4, 2))

as.vector(apply(df, 1, \(x) ifelse(abs(x[1] - x[2:4]) < 2, 1, 0)))
#>  [1] 0 0 1 1 0 1 1 1 1 1 1 0