CODEWITHSUNDEEP
r
Juanmac
Juanmac

Reputation: 35

How does the all function work in R using two expressions?

I have an issue with the all function in R.

let a and b two vectors:

a <- c(Inf,0)

b <- c(1,0)

When I try to evaluate the expression all(a==b) the function returns FALSE, is OK, if it is evaluated the expression all(a==Inf) the function returns FALSE, so far all is working OK, but if I try to evaluate the expression all((a==b) | (a==Inf)) the function returns TRUE.

Could someone explain me why?

Upvotes: 2

Views: 46

Answers (2)

Waldi
Waldi

Reputation: 41240

The OR is done column wise:

a <- c(Inf,0)
b <- c(1,0)

(a==b) 
#> [1] FALSE  TRUE
(a==Inf)
#> [1] TRUE   FALSE
(a==Inf)|(a==b) 
#> [1] TRUE   TRUE

In each column there's a TRUE so each column is TRUE

Upvotes: 2

ThomasIsCoding
ThomasIsCoding

Reputation: 102251

When you type help("|"), you will see that | is element-wise OR.

In this case, given

> (a == b)
[1] FALSE  TRUE

> (a == Inf)
[1]  TRUE FALSE

the expression (a == b) | (a == Inf) is equivalent to

c(FALSE, TRUE) | c(TRUE, FALSE)

and the resultant logic array is c(TRUE, TRUE), which gives you TRUE when you apply all over it.

Upvotes: 2

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