当（A）是R中data.frame的特定条件时，如何使函数获得平均值（B）

Question

this is for setting

#this is for setting

A <- c(1,1,2,2,2,3,4,4,5,5,5)
B <- c(1:10)
C <- c(11:20)

ABC <- data.frame(A,B,C)

#so, I made up my own ABC like this    

   A  B  C
1  1  1 11
2  1  2 12
3  2  3 13
4  2  4 14
5  2  5 15
6  3  6 16
7  4  7 17
8  4  8 18
9  5  9 19
10 5 10 20

On this setting, I want to know, when (A) are in a specific condition, how to get average (B)or(C)

For example if condition(A) are 2:4, get mean (B), and mean(C)

new_ABC <- subset(ABC, ABC$A >= 2 & ABC$A <= 4)
mean(newABC$B)
mean(newABC$C)

and it works.

But if I want to make a function like this, I tried severe days, I have no idea...

getMeanB <- function(condition){
    for(i in min(condition) : max(condition){
        # I do not really know what to do..
    }
}

Any helps will very thanks!!

Answer 1

If the argument 'condition' is a vector , then we can do it

getMean <- function(data, condition, cName) {
    minC <- min(condition)
    maxC <- max(condition)
    i1 <- data[[cName]] >= minC & data[[cName]] <= maxC
   colMeans(data[i1,setdiff(names(data), cName)], na.rm = TRUE)
}

getMean(ABC, 2:4, "A")
#   B    C 
#  5.5 15.5 

NOTE: Here, the 'data' and 'cName' arguments are added to make it more dynamic and applied to other datasets with different column names.