[R] how to judge a virable is a integer?

[S Ellison]

> 3. all.equal(a, as.integer(a))

Closer, but be aware that all.equal will not always return TRUE or FALSE and - more importantly - as.integer truncates towards zero and does NOT generally round to the nearest integer.

a <- 4 - sqrt(2)^2 #Analytically 2
all.equal(a, as.integer(a))
# [1] "Mean relative difference: 0.5"
#because
as.integer(a)
# [1] 1

To return FALSE from all.equal, wrap it in something like

if(all.equal(a, round(a))==TRUE) TRUE else FALSE


S


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