Subsetting Data
On Apr 28, 2011, at 3:38 PM, David Winsemius wrote:
On Apr 28, 2011, at 3:13 PM, Abraham Mathew wrote:
I'm using the subset() function in R. dat <- data.frame(one=c(6,7,8,9,10), Number=c(5,15,13,1,13)) subset(dat, Number >= 10) However, I want to find the number of all rows who meet the Number>=10 condition. I've done this in the past with something like colSums or rowSums or another similar function. But I don't remember how to get the number of elements which meet that condition. function(subset(dat, Number >= 10)) #function is what i'm asking about
Daily's answer would work but if you wanted a direct answer to your question then try nrow or NROW:
nrow(subset(dat, Number >= 10))
[1] 3
NROW(subset(dat, Number >= 10))
[1] 3 There is a difference and I am under the impression that NROW is safer in some way.
> NROW function (x) if (is.array(x) || is.data.frame(x)) nrow(x) else length(x) So if you were doing something with tapply or a [,] subsetting operation which might return a single dimensioned result you would definitely want NROW.
In the above example, I'd run get 3 because there are 3 Number values greater than 10.
-- David Winsemius, MD West Hartford, CT
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David Winsemius, MD West Hartford, CT