calculate mode in R wrt other column

Question

This question is not duplicate of following question : Is there a built-in function for finding the mode? Is there a built-in function for finding the mode? All the answers mentioned on above link find mode for a single column or a vector. Whereas I want to find mode wrt to other column

I have data like this :-

Col1 Col2
C    High
B    Small
C    Medium
B    High
D    Medium
B    Medium
B    Small
B    Medium
B    Small
B    High
B    Small
C    Medium
B    Medium
D    High
B    Small
B    High
D    High

I want to find mode and result should look as follows:-

col1  Mode 
B     Small
C     Medium
D     High

Any help?

Thanks

Could you explain a bit more what you actually try to achieve? I can't understand how you got that result without further explanation. — SaschaM78, Feb 25 '16 at 09:53
which value from col2 occurs maximum number of time for each unique value in col1. Like for B, Value small occurred maximum number of times . Similarly for C and D — r4sn4, Feb 25 '16 at 10:11

score 3 · Answer 1 · edited Feb 25 '16 at 10:06

3

library(data.table)
df[,.(Mode = names(which.max(table(Col2)))), by = Col1]

   Col1   Mode
1:    C Medium
2:    B  Small
3:    D   High

Very similar solution, will just leave it here for reference.

edited Feb 25 '16 at 10:06

Jaap

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answered Feb 25 '16 at 09:58

statespace

1,644
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1

You could also do this in base R: `aggregate(Col2 ~ Col1, data = df, function(x) names(which.max(table(x))))` – Jaap Feb 25 '16 at 10:06
@jaap thanks . simplest solution – r4sn4 Feb 25 '16 at 10:42

score 2 · Accepted Answer · answered Feb 25 '16 at 09:46

2

Using data.table library:

library(data.table)

dt <- as.data.table(df)
dt[, .N, by = list(Col1, Col2)][, .SD[which.max(N)], by = Col1]

answered Feb 25 '16 at 09:46

danas.zuokas

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calculate mode in R wrt other column

2 Answers2