R - Passing a vector argument to reference columns of a data frame in a function

Question

Here is an example of the problem I am trying to solve.

I have a data frame

x<-matrix(1:9, nrow= 3, ncol= 3)
y<-c(1,100,2)
z<-c("A","B","C","D")
df<-cbind(x,y)
colnames(df)<-z 

     A B C  D
[1,] 1 4 7 1
[2,] 2 5 8 100
[3,] 3 6 9 2

For each row, I want to calculate distance between each of the values in A,B, and C with D to find the two values from A, B and C closest to D.

This was my latest attempt.

test<-function(x,y,z){
  d<-abs(x-y)
  df<-data.frame(z,d)
  df<-df[order(d),]
  d<-c(df[1:2,1])
  d<-paste(d[1],"-",d[2],sep="")
}



results<adply(test, 1, transform, res = test(
  c("A","B","C"),D,1:3]))

This is the error I am getting

Error in splitter_a(.data, .margins, .expand, .id) : Invalid margin

I am wanting the result to be a data frame like this:

     A B C  D res
[1,] 1 4 7 25 A-B
[2,] 2 5 8 26 C-B
[3,] 3 6 9 27 A-B

Any help provided is greatly appreciated.

NT

Edit - The suggested answer worked in my test case, but does not work when translated to me real scenario. Here is a sample of the DF

    0%      25%     50%      75%   100% target
1 350.00 350.0000 380.610 380.6100 416.25  425.0
2 350.00 350.0000 350.000 350.0000 350.00  425.0
3 223.83 383.6800 414.890 472.3050 529.20  425.0
4 442.36 442.9625 443.565 444.1675 444.77  472.8
5 466.00 525.4800 529.200 529.2000 529.20  465.6
6 350.00 357.1650 364.330 371.4950 378.66  513.6

This is how the script translates to me scenario

apply(DF, 1, function(x){
  paste(c("0%","25%","50%","75%","100%")[order(abs(x[c(columns[1:5])] - x["target"]))][1:2], collapse = "-")
})

I am getting the following error:

Error in x[c(columns[5:9])] - x[target] : 
  non-numeric argument to binary operator

I have confirmed the data values are numeric

Answer 1

apply(df, 1, function(x){
    paste(c("A", "B", "C")[order(abs(x[c("A", "B", "C")] - x["D"]))][1:2], collapse = "-")
})
#[1] "A-B" "C-B" "A-B"

UPDATE

#DATA
df = read.table(strip.white = TRUE,
                stringsAsFactors = FALSE,
                header = TRUE,
                check.names = FALSE,
                text = "0%      25%     50%      75%   100% target
                1 350.00 350.0000 380.610 380.6100 416.25  425.0
                2 350.00 350.0000 350.000 350.0000 350.00  425.0
                3 223.83 383.6800 414.890 472.3050 529.20  425.0
                4 442.36 442.9625 443.565 444.1675 444.77  472.8
                5 466.00 525.4800 529.200 529.2000 529.20  465.6
                6 350.00 357.1650 364.330 371.4950 378.66  513.6")

apply(df, 1, function(x){
    paste(names(x)[order(abs(x[1:5] - x[6]))][1:2], collapse = "-")
})
#         1          2          3          4          5          6 
#"100%-50%"   "0%-25%"  "50%-25%" "100%-75%"   "0%-25%" "100%-75%"