In R, if you test a condition on a vector instead of a scalar, it will return a vector containing the result of the comparison for each value in the vector. For example...
> v <- c(1,2,3,4,5)
> v > 2
[1] FALSE FALSE TRUE TRUE TRUE
In this way, I can determine the number of elements in a vector that are above or below a certain number, like so.
> sum(v > 2)
[1] 3
> sum(v < 2)
[1] 1
Does anyone know how I can determine the number of values in a given range? For example, how would I determine the number of values greater than 2 but less th开发者_运维百科an 5?
Try
> sum(v > 2 & v < 5)
There are also the %<% and %<=% comparison operators in the TeachingDemos package which allow you to do this like:
sum( 2 %<% x %<% 5 )
sum( 2 %<=% x %<=% 5 )
which gives the same results as:
sum( 2 < x & x < 5 )
sum( 2 <= x & x <= 5 )
Which is better is probably more a matter of personal preference.
Use which:
set.seed(1)
x <- sample(10, 50, replace = TRUE)
length(which(x > 3 & x < 5))
# [1] 6
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