Summarize by two or more attributes

Marc, 
  How could I also apply the spline function to each of the 'columns' found in the result   from 

tapply(Df$Rate,list(Df$Bin,Df$Type),sum)

??




-----Original Message-----
From: Marc Schwartz [mailto:marc_schwartz at me.com] 
Sent: Tuesday, May 17, 2011 12:42 PM
To: ROLL Josh F
Cc: r-help at r-project.org
Subject: Re: [R] Summarize by two or more attributes

I will hit my own ball on this one


tapply(Df$Rate,list(Df$Bin,Df$Type),sum)

Aha....you had mentioned creating a new column in your initial post, presumably added to 'Df', as opposed to creating a new independent matrix of the results.

Your output above creates a 5 x 2 matrix of the resultant sums, one column per 'Type' and one row for each 'Bin'.

The use of ave(), now based upon your above:

  ave(Df$Rate, list(Df$Bin, Df$Type), FUN = sum)

would yield a vector of length 20, which could then be added to the original 'Df' as a new column. The vector would be ordered in such a fashion as to match up with the original rows, based upon Bin and Type.

I am tempted to quote a famous line from Cool Hand Luke, but I'll leave that for now...  :-)

Regards,

Marc Schwartz