检查两列的条件，如果为true，则操纵R中的第三列

Question

I am been searching for an solution to this problem and have not been able to find one. It is somewhat similar to other questions so if this is a duplicate I apologize.

I am looking to check two conditions on a dataframe and when both conditions are met change a third column. It may be easier to see with an example:

greetings <- c("Hello", "Howdy", "Hola")

df <- data.frame(
  Criteria_1 = c("Hello", "Hello", "Goodbye", "Goodbye", "Hello"),
  Criteria_2 = c("Yes", "No", "Yes", "No", "Yes"),
  Change_col = c(1,5,6,9,3))

 Criteria_1 Criteria_2 Change_col
1      Hello        Yes          1
2      Hello         No          5
3    Goodbye        Yes          6
4    Goodbye         No          9
5      Hello        Yes          3

I would like to check if Criteria_1 has a value in the variable 'greeting' and if Criteria_2 is 'Yes'. When both are true I would like to change the value in 'Change_col' to 10.

This is what I tried but it is changing all of the Change_col values to 10.

if(df$Criteria_1 %in% greetings & df$Criteria_2 == 'Yes'){
  df$Change_col <- '10'

I think I may have to use the apply function? But not really sure how to do that. The desired output would be this:

  Criteria_1 Criteria_2 Change_col
1      Hello        Yes         10
2      Hello         No          5
3    Goodbye        Yes          6
4    Goodbye         No          9
5      Hello        Yes         10

Answer 1

We can use a logical expression to change the values in 'Change_col' to 10

df$Change_col[with(df, Criteria_1 %in% greetings & Criteria_2 == "Yes")] <- 10
df
#  Criteria_1 Criteria_2 Change_col
#1      Hello        Yes         10
#2      Hello         No          5
#3    Goodbye        Yes          6
#4    Goodbye         No          9
#5      Hello        Yes         10

Answer 2

I think dplyr::mutate and the ifelse() statement offers a nice solution. Have you tried the following?

library(tidyverse)

newDf <- df %>%
   mutate(Change_col = ifelse(Criteria_1 %in% greetings & Criteria_2 == "Yes", 10, Change_col))