we found a surprising result from basic code in R. We search for answers online but found nothing.
Does anyone knows the reason of this result?

the following code generates a fake data.frame

z2 <- data.frame(a=rep(1:120,100), b=rep(rep(c(0,1),each=120),50), c=rep(rep(c(0,1),each=240),25), d=rep(rep(seq(.1,2.5,.1),each=120),4)

we want the subset of z2 having d==1.5, but the result is an empty data.frame.

subset(z2,d==1.5) [1] a b c d <0 rows> (or 0-length row.names)

however, the value 1.5 is present in the dataframe

z2[7750,] a b c d 7750 70 0 0 1.5

but simple functions do not work:

table(z2$d==1.5) FALSE 12000

can anyone say what the h*** has happened ? please help, my head has exploded XD

G.M.