Re: [s-news] S-News Daily Digest V2 #1954

[Doug Bolgiano <dougb@psbcresearch.org>]

extracting components from a list of lists

I use tapply with the acf function (lag =3) and the subject index of a data frame to calculate autocorrelations for a variable measured repeatedly on each subject (n = 180).  The result is a list of lists (which are the output of the acf function), one for each subject.  I want to extract the $acf component from each subject's list and form a matrix where rows index subjects and columns index lags.  

I have tried using the subscript operators [] and [[ ]] to extract the acf componets.  Do I have to resort to looping through the subject lists and extracting the acf component from each list individually or is there a more efficient way to do this?

Doug Bolgiano
Puget Sound Blood Center
Seattle, WA  98104