基于其他列的变量赋值

Question

假设我有这个data.frame：

tdata <- structure(list(fyear = c("1971", "1971", "1971", "1971", "1971", 
"1971", "1971", "1971", "1971", "1971", "1971", "1971", "1972", 
"1972", "1972", "1972", "1972", "1972", "1972", "1972", "1972", 
"1972", "1972", "1972", "1972", "1973", "1973", "1973", "1973", 
"1973", "1973", "1973", "1973", "1973", "1973", "1973", "1973", 
"1974", "1974", "1974", "1974", "1974", "1974", "1974", "1974", 
"1974", "1974", "1974", "1974", "1975", "1975", "1975", "1975", 
"1975", "1975", "1975", "1975", "1975", "1975", "1975")), class = c("tbl_df", 
"tbl", "data.frame"), row.names = c(NA, -60L), .Names = "fyear")

如果tdata$check，我想将1分配给fyear == 1975。我试过这个if语句，但是它引发了一个错误

if(tdata$fyear == 1975)) tdata$check <- 1

错误：

Warning message:
In if (ex$fyear == 1975) ex$check <- 1 :
  the condition has length > 1 and only the first element will be used

Answer 1

试试这个

tdata$check <- (tdata$fyear==1975)*1

Answer 2

上面的布尔方法很聪明，但要分配任何值：

tdata$check[tdata$fyear==1975] <- 1

如果你想要0而不是NAs

tdata$check <- 0
tdata$check[tdata$fyear==1975] <- 1

Answer 3

或者

tdata$check[tdata$fyear==1975]<-1

产生一列1（如果为真）或NA，如果不是真的话。