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I am looking to find the summary statistics (mean and potentially standard deviation and other quantities) of a vector (column) in a data frame, but grouped. I hope to group the statistics by another categorical variable

I know that one find summary as 

summary(data$rating)

however I am not sure how I find summary statistics for gender separately.

I tried 

summary(data$rating, data$gender)

but that does give my anything but summary(data$rating)

marc_s
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pkpkPPkafa
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2 Answers2

0

You could also use the by function:

by(data$rating, data$gender, summary)
cimentadaj
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Use tapply() or aggregate():

data <- data.frame(rating = 100*runif(30), 
                   gender=sample(c("female","male"),30, replace=TRUE))

tapply(data$rating, data$gender, summary)

aggregate(data$rating, by=list(data$gender), 
      FUN=function(x) cbind(mean(x), median(x), sd(x)))
Bernhard
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