R: How to generate vectors of highest value in each row?

Question

Let's say that my data frame contains

> DF
   V1   V2   V3  
1  0.3  0.4  0.7  
2  0.4  0.2  0.1  
3  0.2  0.8  0.3  
4  0.5  0.8  0.9   
5  0.2  0.7  0.8  
6  0.8  0.3  0.6  
7  0.1  0.5  0.4

the rows would be the different types of automobiles, and the columns would be the probabilities for a given category of V1, V2, V3.

I want to generate a vector that assigns to each automobile the category of which it has the highest probability in. For example, I'd want automobile 1 to be associated with V3, automobile 2 to be associated with V1, automobile 3 to be associated with V2.

Any aids or hints on how I should tackle this?

akrun · Accepted Answer · 2016-05-15T08:58:24.900

4

We can use max.col to get the column index that corresponds to the largest value in each row.

names(DF)[max.col(DF, "first")]
#[1] "V3" "V1" "V2" "V3" "V3" "V1" "V2"

edited May 15 '16 at 08:58

answered May 15 '16 at 08:43

akrun

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1

Thanks! that was a quick and easy – Elizabeth May 15 '16 at 21:50

score 2 · Answer 2 · answered May 15 '16 at 09:12

2

Another solution is:

names(DF)[apply(DF, 1, which.max)]
# [1] "V3" "V1" "V2" "V3" "V3" "V1" "V2"

answered May 15 '16 at 09:12

FlorianSchunke

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R: How to generate vectors of highest value in each row?

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