Hello: I would like to sum every x columns of a dataframe for each row. For instance, if x is 10, then for dataframe df, this function will sum the first ten elements together and then the next ten:
sapply(list(colnames(df)[1:10], colnames(df)[11:20]),function(x)apply( df[,x], 1, sum)) If the number of columns is quite large (1000's), then manually entering the list above is not practical. Any suggestions? I would also like to do a variant of the above, where I sum every nth element. Thanks, Michael ------------------------------------------------------------------------------ Michael I. Westphal, PhD Africa Region Water Resources (AFTWR) South Asia Region Sustainable Development (SASSD) World Development Report 2010: "Development in a Changing Climate" www.worldbank.org/wdr2010 Room J6-007 (mail stop: J6-603) Tel: 202.473.1217 The World Bank 1818 H St NW, Washington DC 20433, USA ______________________________________________ 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.
