Apply a calculation to multiple columns

Question

I've got a table with n columns. I'd like to find the largest value in each column, and then return the value from column CAG that's in the same row. I've managed to do this for column A01, but can you help me apply across all columns?

#My data frame
data <- data.frame(CAG = c(13, 14, 15), A01 = c(6485,35,132), A02 = c(0,42,56))

#My function# applied to work with column A01
result <- data$CAG[data$'A01' == max(data$'A01')]

Possible duplicate of [for each row, return the column name of the largest value](https://stackoverflow.com/questions/17735859/for-each-row-return-the-column-name-of-the-largest-value) — lebelinoz, Jun 23 '17 at 06:04

score 1 · Accepted Answer · answered Jun 23 '17 at 05:47

1

You want which.max. Apply it to all columns using sapply.

> data[sapply(data[2:ncol(data)], which.max), ]$CAG
[1] 13 15

answered Jun 23 '17 at 05:47

Roman Luštrik

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Brilliant thank you, that works perfectly. Very neat and simple! – Mike Jun 23 '17 at 09:43
A minor variant is `data$CAG[sapply(data[-1], which.max), ]`. – lmo Jun 23 '17 at 12:33

Apply a calculation to multiple columns

1 Answers1