CODEWITHSUNDEEP
rapply
John
John

Reputation: 31

How do I get which.max to return the row name and not an index number

After running correlations I need to ID the row of the maximum value in each column. I am using which.max but I can not get the row name. Instead I get an index number which is worthless. Each row has a name.

apply(my.data,2,which.max)

Upvotes: 3

Views: 9127

Answers (2)

Rich Scriven
Rich Scriven

Reputation: 99331

The result from running correlations should be a matrix, so here's an example using a matrix.

> M <- matrix(c(1,5,3,17,6,8,9,2,3,10,8,4), 4, 3)
> rownames(M) <- letters[1:4]
> M
##   [,1] [,2] [,3]
## a    1    6    3
## b    5    8   10
## c    3    9    8
## d   17    2    4
> rownames(M)[apply(M, 2, which.max)]
## [1] "d" "c" "b"

Upvotes: 1

lukeA
lukeA

Reputation: 54237

# create example data
set.seed(1)
df <- data.frame(col1=runif(100), col2=runif(100))
row.names(df) <- paste0("row", 1:100)

# get max
rownames(df[apply(df, 2, which.max), ])
# [1] "row18" "row4"

Upvotes: 7

Related Questions