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.
