[R] tapply output

[Peter Ehlers]

On 2010-10-06 13:24, Erik Iverson wrote:
> Hello,
>
> You can use ddply from the very useful plyr package to do this.
> There must be a way using "base R" functions, but plyr is
> worth looking into in my opinion.
>
>   >  install.packages("plyr")
>   >  library(plyr)
>   >  ddply(myData, .(class, group, name), function(x) mean(x$height))
>
>     class group name   V1
> 1     0     A  Tom 62.5
> 2     0     B Jane 58.5
> 3     1     A Enzo 66.5
> 4     1     B Mary 70.5

Or use summarize:

  >  ddply(myData, .(class, group, name), summarize, mht = mean(height))

   -Peter Ehlers

>
> Geoffrey Smith wrote:
>> Hello, I am having trouble getting the output from the tapply function
>> formatted so that it can be made into a nice table.  Below is my question
>> written in R code.  Does anyone have any suggestions?  Thank you.  Geoff
>>
>> #Input the data;
>> name<- c('Tom', 'Tom', 'Jane', 'Jane', 'Enzo', 'Enzo', 'Mary', 'Mary');
>> year<- c(2008, 2009, 2008, 2009, 2008, 2009, 2008, 2009);
>> group<- c('A', 'A', 'B', 'B', 'A', 'A', 'B', 'B');
>> class<- c(0, 0, 0, 0, 1, 1, 1, 1);
>> height<- c(62, 63, 59, 58, 67, 66, 70, 71);
>>
>> #Combine the data into a data frame;
>> myData<- data.frame(name, year, group, class, height);
>> myData;
>>
>> #Calculate the mean of height by class, group, and name;
>> tapply(myData$height, data.frame(myData$class, myData$group, myData$name),
>> mean);
>>
>> #The raw output from the tapply function is fine, but I would;
>> #really like the output to look like this;
>> #  class   group     name     mean
>> #    0       A            Tom        62.5
>> #    0       B            Jane        58.5
>> #    1       A            Enzo       66.5
>> #    1       B            Mary       70.5
>>
>
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