I have a data frame that I am trying to group and then sum based on two columns. The two columns are characters with one being month and the other variable.

The following is a sample of the data frame and structure.

#row.names month variable amount 1 1-Jan x 1000 2 1-Jan x 3000 3 2-Feb z 5000 4 2-Feb y 3000 

I tried to group the data first and then I was going to try to summarise, however I am unable to get group_by_() to do the trick. Below is the code I tried.

byVarMonth <- group_by_(df, variable, (as.date(month)))

Thanks for the help.

2

2 Answers

You apparently are not interested in taking your Character [month] as a Date variable. Considering that I'm not wrong you could simply do something like this:

library(dplyr)
tab %>% group_by(month, variable) %>% summarise(a_sum=sum(amount), a_mean=(mean(amount)))

and get this:

Source: local data frame [3 x 4]
Groups: month month variable a_sum a_mean
1 1-Jan x 4000 2000
2 2-Feb y 3000 3000
3 2-Feb z 5000 5000

... or, you can use an alternative sintax:

summarise(group_by(df, variable), sum(amount), mean(amount))

Enjoy.

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