which(abs(v - .1) <= .Machine$double.eps)
seems to me too cumbersome to write. Any other easier way? all.equal
does not quite work
Nikhil
On Jun 9, 2010, at 7:54 AM, Petr PIKAL wrote:
Hi
r-help-boun...@r-project.org napsal dne 09.06.2010 13:16:40:
Dear R community,
I am puzzled by the following lines:
v <- seq(-0.5,0.5,by=0.1)
v
[1] -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5
which(v == -0.4)
[1] 2
which(v == 0)
[1] 6
which(v == 0.1)
integer(0)
which(v == 0.2)
integer(0)
which(v == 0.3)
integer(0)
which(v == 0.4)
[1] 10
which(v == 0.5)
[1] 11
Why "which" can only match some of the values in "v"? Are the numbers
generated by "seq" not exact fractional numbers?
Please, help me to understand this.
Well FAQ 7.31 was not here some time. Computing in binary results in
finite precision of fractional numbers.
v <- seq(-0.5,0.5,by=0.1)
v[7]-0.1
[1] 8.326673e-17
Regards
Petr
J
Dr James Foadi PhD
Membrane Protein Laboratory (MPL)
Diamond Light Source Ltd
Diamond House
Harewell Science and Innovation Campus
Chilton, Didcot
Oxfordshire OX11 0DE
Email : james.fo...@diamond.ac.uk
Alt Email: j.fo...@imperial.ac.uk
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