IF ELSE语句中的多个动作

Question

A sample data frame looks like this:

df = data.frame(a=1:5, b=11:15)
a  b
1 11
2 12
3 13
4 14
5 15

How do I use if else statement to create new column c and d in the data frame? I want the output to look like this:

a b    c    d
1 11 'yes'  22
2 12 'yes'  24
3 13 'yes'  26
4 14 'no'   14
5 15 'no    15

I've tried this according to ( If statement with multiple actions in R )!

for (i in nrow(df)){
  if (df$a[i] <4) {
    df$c[i] = 'yes'; 
    df$d[i] = df$b[i]*2;
    df
  } else {
    df$c[i] = 'no'; 
    df$d[i] = df$b[i];
    df
  }
}

But the output only provide the last row:

 a  b   c  d
 1 11 <NA> NA
 2 12 <NA> NA
 3 13 <NA> NA
 4 14 <NA> NA
 5 15   no 15

Thanks in advance.

Answer 1

Another vectorized solution using ifelse() :

df$c <- ifelse(df$a < 4, 'yes', 'no')
df$d <- ifelse(df$a < 4, df$b*2, df$b)