关于 R 中 3 个条件的 if 语句

Question

I see some issues in my if statement. The output I get is wrong than what i expected.

asd <- data.frame(a = c(-16,-9,-48,20,-39), b = c(2, -4, -2, 2, 4), c = c(9, -14, 23, -13, -6))
if(asd$a < 0 && asd$b>0 && asd$c>0){
  asd$d <- "Inv"
} else {
  asd$d <- "NotInv"
}
> asd
    a  b   c   d
1 -16  2   9 Inv
2  -9 -4 -14 Inv
3 -48 -2  23 Inv
4  20  2 -13 Inv
5 -39  4  -6 Inv

Expected output

> asd
    a  b   c   d
1 -16  2   9 Inv
2  -9 -4 -14 Not Inv
3 -48 -2  23 Not Inv
4  20  2 -13 Not Inv
5 -39  4  -6 Not Inv

Answer 1

with base R :

asd$d <- "Not Inv"
asd$d[asd$a < 0 & asd$b>0 & asd$c>0] <- "Inv"
asd

    a  b   c       d
1 -16  2   9     Inv
2  -9 -4 -14 Not Inv
3 -48 -2  23 Not Inv
4  20  2 -13 Not Inv
5 -39  4  -6 Not Inv

with dplyr :

library(dplyr)
asd %>% mutate(d = if_else(a < 0 & b>0 & c>0,"Inv","Not Inv"))

    a  b   c       d
1 -16  2   9     Inv
2  -9 -4 -14 Not Inv
3 -48 -2  23 Not Inv
4  20  2 -13 Not Inv
5 -39  4  -6 Not Inv

You got a wrong result because you used && instead of & :

asd$a < 0 && asd$b>0 && asd$c>0
[1] TRUE

Meaning that only if statement is executed:

asd$d <- "Inv"

Using & instead gives the expected vectorized result:

asd$a < 0 & asd$b>0 & asd$c>0
[1]  TRUE FALSE FALSE FALSE FALSE