Setting value based on another column in dataframe

Question

I have the following data frame:

A  P(A)
1  0.8
0  0.7
1  0.5
1  0.8
1  0.9
0  0.7
0  0.8

For all 0's in column A, I would like to calculate 1-P(A). This would give me the following dataset:

A  P(A)
1  0.8
0  0.3  ## 1 - 0.7
1  0.5
1  0.8
1  0.9
0  0.3  ## 1 - 0.7
0  0.2  ## 1 - 0.8

I tried this but it doesn't give me the required output.

  for(i in nrow(results)) {
    if(results[i,1]==0) {
      results[i,2]<- 1-results[i,2] 
    }
  }

How is this possible in R?

Do you want those values as another column in the same data frame? And you want the result of the calculation, right, not an equation for it? — ulfelder, Nov 12 '15 at 20:57
`with(DF, \`P(A)\`^A*(1-\`P(A)\`)^(1-A))` similar to any other programming language... As you can see, `P(A)` is a bad name for a column... There's also `dbinom(DF$A, size=1, prob=DF$\`P(A)\`)` — Frank, Nov 12 '15 at 20:59

Jacob H · Answer 1 · 2015-11-13T03:10:38.210

1

df <- data.frame(A = c(1,0,1,1,1,0,0), P = c(0.8, 0.7, 0.5,0.8, 0.9,0.7,0.8))

df[df$A == 0, "P" ] <- 1 - df[df$A == 0, "P"]

edited Nov 13 '15 at 03:10

answered Nov 12 '15 at 21:08

Jacob H

1

@Frank just fixed it. That is what I get for not testing it first. – Jacob H Nov 12 '15 at 23:05

1 Answers1