Home summarizing counts of a factor with dplyr
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summarizing counts of a factor with dplyr

user1417
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user1417 Published in June 25, 2018, 12:03 am

I want to group a data frame by a column (owner) and output a new data frame that has counts of each type of a factor at each observation. The real data frame is fairly large, and there are 10 different factors.

Here is some example input:

library(dplyr)
df = tbl_df(data.frame(owner=c(0,0,1,1), obs1=c("quiet", "loud", "quiet", "loud"), obs2=c("loud", "loud", "quiet", "quiet")))

  owner  obs1  obs2
1     0 quiet  loud
2     0  loud  loud
3     1 quiet quiet
4     1  loud quiet

I was looking for output that looks like this:

out = data.frame(owner=c("0", "0", "1", "1"), observation=c("obs1", "obs2", "obs1", "obs2"), quiet=c(1, 0, 1, 2), loud=c(1, 2, 1, 0))

  owner observation quiet loud
1     0        obs1     1    1
2     0        obs2     0    2
3     1        obs1     1    1
4     1        obs2     2    0

Melting gets me partway there:

melted = tbl_df(melt(df, id=c("owner")))

  owner variable value
1     0     obs1 quiet
2     0     obs1  loud
3     1     obs1 quiet
4     1     obs1  loud
5     0     obs2  loud
6     0     obs2  loud
7     1     obs2 quiet
8     1     obs2 quiet

But what's the last step? If 'value' was a numeric, I'd just go:

melted %>% group_by(owner, variable) %>% summarise(counts=sum(value))

Thanks so much!

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