On Sep 8, 2011, at 8:21 PM, Adam Pridgen wrote:
Hello,
I am trying to pass a conditional expression into an expression to be
evaluated when ever an R statement is called. For example:
get_unique_count <- function(df, select, field){
uniqs <- unique(subset(df, select)[field])
return (nrow(uniqs))
}
In this case select is a conditional statement year == 1980, and the
function would be called in the following manner:
library(ggplot2)
get_unique_count(mpg, year==1980, 'manufacturer')
Borrowing heavily from subset.data.frame:
get.uniq <- function (x, logic.expr, field)
{
e <- substitute(logic.expr)
r <- eval(e, x, parent.frame())
if (!is.logical(r))
stop("'subset' must evaluate to logical")
r <- r & !is.na(r)
if (missing(field))
vars <- TRUE
else {
nl <- as.list(seq_along(x))
names(nl) <- names(x)
vars <- eval(substitute(field), nl, parent.frame())
}
uniqs <- unique(x[r, field, drop = FALSE])
NROW(uniqs)
}
Thank for any help in advance,
-- Adam
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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David Winsemius, MD
Heritage Laboratories
West Hartford, CT
______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
