I think Simon has provided a good answer to the actual question but as a refugee from SAS I'd suggest having a look at www.et.bs.ehu.es/~etptupaf/pub/R/RforSAS&SPSSusers.pdf or getting the book Muenchen, R. A. (2008). R for SAS and SPSS Users (1st ed.). Springer.
R ans SAS approach things very differently at times. John Kane Kingston ON Canada > -----Original Message----- > From: thoms...@email.arizona.edu > Sent: Mon, 7 Jan 2013 19:17:27 -0600 > To: r-help@r-project.org > Subject: [R] Conditional Statistics > > Hello, > > I am a new user of R. I am coming from SAS and do statistics on stock > market data, economic data, and social data. My question is this: How > can you get the mean, standard dev, etc. of a variable based on a > conditional statement on either the same variable or a different > variable in the same data set? So if I had the closing prices of the > S&P from 01/01/1990-12/31/1990, how could I get the average price of > the S&P from 02/01/1990-03/15/1990? Or the average price of the S&P on > Mondays (assuming a dummy var is created for 1 = Monday, 0 = else). I > understand that you can create subsets and new data sets based on the > conditional statements; but is there an easier way to do this by > typing a line into the mean() statement? That was extremely easy in > SAS where you could say: > > proc means data=sp500; > var price; > where monday = 1; > > Thank you for your help. > > Joe > > ______________________________________________ > R-help@r-project.org 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. ____________________________________________________________ FREE 3D MARINE AQUARIUM SCREENSAVER - Watch dolphins, sharks & orcas on your desktop! ______________________________________________ R-help@r-project.org 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.
