问题
For each row in a data frame I want to copy a value from one column to another depending on a value in third column.
I tried to do it with a combined for loop and if function:
## example
condition <- c("1","2","2","1","2","","3","3")
SZ01 <- c("1","1","1","1","1","","1","1")
SZ02 <- c("2","2","2","2","2","","2","2")
SZ03 <- c("3","3","3","3","3","","3","3")
df <- data.frame(cbind(condition,SZ01,SZ02,SZ03), stringsAsFactors = FALSE)
df$retribution <- NULL
df$special_prevention <- NULL
df$general_prevention <- NULL
for (i in 1:length(df$condition)){
if (df$condition[i] == 1){
df$retribution[i] <- df$SZ01[i]
df$special_prevention[i] <- df$SZ02[i]
df$general_prevention[i] <- df$SZ03[i]
}else if (df$condition[i] == 2) {
df$retribution[i] <- df$SZ02[i]
df$special_prevention[i] <- df$SZ03[i]
df$general_prevention[i] <- df$SZ01[i]
}else if (df$condition[i] == 3) {
df$retribution[i] <- df$SZ03[i]
df$special_prevention[i] <- df$SZ01[i]
df$general_prevention[i] <- df$SZ02[i]
} else {
df$retribution[i] <- "missing_condition"
df$special_prevention[i] <- "missing_condition"
df$general_prevention[i] <- "missing_condition"
}
}
This seems to work (no error message), but looking at my data there must be something wrong.
For example row 1 has condition == 1. This means, that for this row df$retribution should receive the same value as the one in row 1 of df$SZ01.
But it doesn't. Is there anyone that can see the mistake I made?
回答1:
Try the following:
condition <- c("1","2","2","1","2","","3","3")
SZ01 <- c("1","1","1","1","1","","1","1")
SZ02 <- c("2","2","2","2","2","","2","2")
SZ03 <- c("3","3","3","3","3","","3","3")
df <- data.frame(cbind(condition,SZ01,SZ02,SZ03), stringsAsFactors = F)
df$retribution <- ifelse(df$condition == "1", df$SZ01,
ifelse(df$condition == "2", df$SZ02,
ifelse(df$condition == "3", df$SZ03, "missing")))
df$special_prevention <- ifelse(df$condition == "1", df$SZ02,
ifelse(df$condition == "2", df$SZ03,
ifelse(df$condition == "3", df$SZ01, "missing")))
df$general_prevention <- ifelse(df$condition == "1", df$SZ03,
ifelse(df$condition == "2", df$SZ01,
ifelse(df$condition == "3", df$SZ02, "missing"))))
Output:
df
condition SZ01 SZ02 SZ03 retribution special_prevention general_prevention
1 1 1 2 3 1 2 3
2 2 1 2 3 2 3 1
3 2 1 2 3 2 3 1
4 1 1 2 3 1 2 3
5 2 1 2 3 2 3 1
6 missing missing missing
7 3 1 2 3 3 1 2
8 3 1 2 3 3 1 2
来源：https://stackoverflow.com/questions/39104617/get-value-from-other-column-based-on-value-of-a-column