Folks, I have a dataframe comprising a column of dates and a column of signals (-1, 0, 1) that looks something like this:
30/01/2007 0 31/01/2007 -1 01/02/2007 -1 02/02/2007 -1 03/02/2007 1 04/02/2007 1 05/02/2007 1 06/02/2007 1 07/02/2007 1 08/02/2007 1 09/02/2007 0 10/02/2007 0 11/02/2007 0 12/02/2007 1 13/02/2007 1 14/02/2007 1 15/02/2007 0 16/02/2007 0 What I need to do is for each signal *in reverse chronological order* to find the date that it first appeared. So, for the zero on 16/02/2007 and 15/02/2007, the 'inception' date would be 15/02/2007, because the day before, the signal was 1. Likewise, the 'inception' date for the signal 1 on 08/02/2007 and the five days prior, would be 03/02/2007. I need to create a structure of inception dates that would finally look as follows: -1 31/01/2007 -1 31/01/2007 -1 31/01/2007 1 03/02/2007 1 03/02/2007 1 03/02/2007 1 03/02/2007 1 03/02/2007 1 03/02/2007 0 09/02/2007 0 09/02/2007 0 09/02/2007 1 12/02/2007 1 12/02/2007 1 12/02/2007 0 15/02/2007 0 15/02/2007 Is there a clever way of doing this? My sadly C-oriented upbringing can only think in terms of for-loops. Thanks! Murali _________________________________________________________________ The average US Credit Score is 675. The cost to see yours: $0 by Experian. ______________________________________________ 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.
