[R] bind mean to a df

[Joshua Wiley]

Hi Geoffrey,

Here is one option (data named dfrm instead of data because data() is
a function too):

## Data
dfrm <- data.frame(
  name = c('Frank','Frank','Frank','Tony','Tony','Tony','Ed','Ed','Ed'),
  year = c(2004,2005,2006,2004,2005,2006,2004,2005,2006),
  sale = c(56,45,55,65,68,70,45,67,23))
## Using with() to avoid typing names and ave() to do the work
dfrm$mean <- with(dfrm, ave(x = sale, name, FUN = mean))
## look at the results
dfrm

Cheers,

Josh

On Mon, Apr 11, 2011 at 8:46 PM, Geoffrey Smith <gps at asu.edu> wrote:
> Hello, I would like to take the mean of a column from a data frame and then
> bind the mean back to the data frame.  I can do this using the following
> lines of code, but I am looking for a more elegant solution.  Thank you very
> much.  Geoff
>
> name <- c('Frank','Frank','Frank','Tony','Tony','Tony','Ed','Ed','Ed');
> year <- c(2004,2005,2006,2004,2005,2006,2004,2005,2006);
> sale <- c(56,45,55,65,68,70,45,67,23);
>
> data <- data.frame(name=name, year=year, sale=sale);
> data;
>
> #is there a more elegant way to add a column of means for sale by name than
> what I did below?;
>
> mean <- data.frame(aggregate(data$sale, list(data$name), mean));
> colnames(mean) <- c('name','mean');
> mean;
>
> data <- merge(data, mean);
> data;
>
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-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/