On 22/06/2007 6:21 PM, Thomas Pujol wrote: > I've read that certain operations performed on a matrix (e.g. ribind, cbind) > are often much faster compared to operations performed on a data frame. > > Other then the "bind functions", what are the main operations that are > significantly faster on a a matrix?
Indexing (e.g. x[1,3]) is much faster on a matrix. > > I know that data frames allow for columnnames and rownames, and that each > column in a data frame can have different data types. Are there any other > advantages of storing data in a a dataframe rather then a matrix? Data frames are lists, so you can use things like df$columnname, with(df, expression), attach(df), etc. Data frame columns have names, but matrices don't necessarily. I'd generally use data frames in any situation where the rows are cases and the columns are characteristics, until I found they were too slow: and then I'd consider temporary conversion to a matrix to speed things up. As Knuth said, premature optimization is the root of all evil. Duncan Murdoch ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
