[R] Calculating the mean of values in tables using formulae
daniel at umd.edu
Sat Jul 23 07:40:45 CEST 2011
Check the *apply() series of functions. tapply() will do what you want.
Mark Alen wrote:
> I know commands like xtabs and table allow a user to do cross-tabulation
> For example the following command generates a pivot table that shows the
> number of cars that have the same number of gears and cylinders.
> cyl 3 4 5
> 4 1 8 2
> 6 2 4 1
> 812 0 2
> We can extend the formula so it could show the sum of the horse power for
> the cars in each bin
> cyl 3 4 5
> 4 97 608 204
> 6 215 466 175
> 82330 0 599
> I am now wondering, is it possible to calculate the mean of horse powers
> for cars in each bin? for example something like
> this xtabs(mean(hp)~cyl+gear, data = mtcars)
> Thank you
> R-help at r-project.org mailing list
> PLEASE do read the posting guide
> and provide commented, minimal, self-contained, reproducible code.
View this message in context: http://r.789695.n4.nabble.com/Calculating-the-mean-of-values-in-tables-using-formulae-tp3688416p3688437.html
Sent from the R help mailing list archive at Nabble.com.
More information about the R-help