[R] Why does a[which(b == c[d])] not work?

[Thomas Bock]

Dear list,

I can not understand why the expression in
the subject does not work correct:

 > dcrn[which(fn == inve[2])]
numeric(0)
 > inve[2]
[1] 406.7
 > dcrn[which(fn == 406.7)]
 [1] 1.3994e-07 1.3988e-07 1.3953e-07 1.3966e-07 1.3953e-07 1.3968e-07

Is this a kick self problem or an bug?

Thaks very much
Thomas