How to subset() from data frame using specific rows
This isn't going to be the most elegant, but it should work: ## Get the factors as characters ff <- as.character(chemdata$site) ## Identify those that match what you want ff <- grepl(ff, "BC-") now use this logical vector to subset chemdata[ff, ] Can't test, but should be good to go assuming that "BC-" entirely identifies those sites you want. If you have other "BC-" things read through the ?regex documentation and I think it describes how to do selective wildcards Michael
On Tue, Oct 4, 2011 at 2:39 PM, Rich Shepard <rshepard at appl-ecosys.com> wrote:
?I have a data frame called chemdata with this structure:
str(chemdata)
'data.frame': ? 14886 obs. of ?4 variables: ?$ site ? ?: Factor w/ 148 levels "BC-0.5","BC-1",..: 104 145 126 115 114 128 124 2 3 3 ... ?$ sampdate: Date, format: "1996-12-27" "1996-08-22" ... ?$ param ? : Factor w/ 8 levels "As","Ca","Cl",..: 1 1 1 1 1 1 1 1 1 1 ... ?$ quant ? : num ?0.06 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ... ?I've looked in the R Cookbook and Dalgaard's intro book without finding a way to use wildcards (e.g., like "BC-*") or explicitly witing each site ID when subdsetting a data frame.. ?I need to create subsets (as data frames) based on sites, but including all sites on each stream. For example, using the initial site factor shown above, I want a subset containing all data for sites "BC-0.5", "BC-1". "BC-2", "BC-3", "BC-4", "BC-5", and "BC-6". Pointers appreciated, Rich
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