如何在 R 中使用应用 function 来查找子组的变量的最大值

Question

 salary <- data.frame(name=c("Kay","Dave","Jon","Jenny","Jim","Eve","Ed"),
 salary=c(60000, 100000, 50000, 80000, 30000, 40000, 20000),
 gender=factor(c("F","M","M","F","M","F","M")))

I am able to filter a female data frame with

femaleFiltered <- salary[ which(salary$gender=='F'), ]

and I am trying to use

getMaxSal1 <- function(x) {
    x[which.max(x$salary),]
}

apply(femaleFiltered,2,getMaxSal1)

but get error "Error in x$salary: $ operator is invalid for atomic vectors"

Answer 1

We can use subset from base R

subset(femaleFiltered, salary == max(salary))
#   name salary gender
#4 Jenny  80000      F

---

Or as per OP's requirement about a possible use of * apply

femaleFiltered[unlist(lapply(names(femaleFiltered), 
       function(nm) which.max(femaleFiltered[nm]$salary))),]
#   name salary gender
#4 Jenny  80000      F

Answer 2

I'd suggest

aggregate(salary$salary, by=list(salary$gender), FUN = max)

oh just read about needing to do an apply function.

Make a list of two data frames, one for males, one for females.

Then use lapply() with FUN = max.

lapply(list(femaleFiltered$salary, maleFiltered$salary), max)