John, Thanks, that works nicely. Didn't know about 'get'.
Onwards and upwards! :-) Cheers, Murali "John James" <[EMAIL PROTECTED]> 29/03/2007 12:40 To <[EMAIL PROTECTED]> cc Subject RE: [R] creating conditional list of elements Murali If sm is your orginal matrix # such that > sm[sm$Enabled,]$Signal [1] "bar_signal" "cif_signal" # and bar_signal <- matrix(rnorm(100), nrow=5, ncol=20) cif_signal <- matrix(rnorm(60), nrow=12, ncol=5) # then... sapply(sm[sm$Enabled,]$Signal, function(x){NROW(get(x))}) bar_signal cif_signal 5 12 Hope this helps John James Mango Solutions -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: 29 March 2007 11:40 Cc: r-help@stat.math.ethz.ch Subject: Re: [R] creating conditional list of elements Sorry to plague the list, but I think I got the answer. The following would do: > signalList <- list(tradingRules$Signal[tradingRules$Enabled]) [[1]] > length(signalList) [1] 2 Now my problem is shifted: I have the Signal column in the original data frame referring to actual matrices previously created in R. That is, bar_signal and cif_signal are extant matrices. What I need is the minimum number of rows in these matrices, so what I plan to do is: > n <- min(sapply(signalList, NROW)) but this doesn't work (it returns 1, but I have 2800 rows in each of bar_signal and cif_signal, so I should get 2800) Is there a smart way to do this? And is there a way to tell R that the entries in the Signal column of tradingSignal are the names of objects? Thanks, Murali Murali Menon/GB/ABNAMRO/NL 29/03/2007 11:13 To r-help@stat.math.ethz.ch cc Subject creating conditional list of elements Folks, I have a matrix as follows (first column is the rownames, first row is the columnnames) Rule Enabled Signal Foo False foo_signal Bar True bar_signal Gum False gum_signal Cif True cif_signal I would like to create a list of only those signals whose 'enabled' flag is True. So in the above case I should end up with signalList = bar_signal, cif_signal Likewise, if the enabled flags were all set to False, then signalList should be an empty list. What's a good way to achieve this, please? Thanks, Murali --------------------------------------------------------------------------- This message (including any attachments) is confidential and...{{dropped}} ______________________________________________ R-help@stat.math.ethz.ch 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. --------------------------------------------------------------------------- This message (including any attachments) is confidential and...{{dropped}} ______________________________________________ R-help@stat.math.ethz.ch 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.