How to subset() from data frame using specific rows
Hi Rich, You can use something like this:
testdata <- c("A1", "A2", "A3", "B1", "B2", "B3")
grep("^A", testdata)
[1] 1 2 3
grepl("^A", testdata)
[1] TRUE TRUE TRUE FALSE FALSE FALSE Sarah
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
Sarah Goslee http://www.functionaldiversity.org