问题
It seems that one of my machines produces wrong results for seq function while another machine or the online r-fiddle (http://www.r-fiddle.org) interpreter give expected results. On the machine in question following happens:
seq(from = 1, to = 1.1, by = 0.01)
[1] 1.0 1.0 1.0 1.0 1.0 1.0 1.1 1.1 1.1 1.1 1.1
Changing the command slightly returns expected result
seq(from = 0.99, to = 1.1, by = 0.01)
[1] 0.99 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10
As soon as I cross the "1" threshold, the wrong result occurs, e.g. same when I do from = 2.95 to = 3.1, etc. Not sure how to find an answer as I couldn't replicate the problem on my other machine or on r-fiddle. The problem persists even after restarting the pc.
R version 3.1.3 (2015-03-09)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 7 x64 (build 7601) Service Pack 1
locale:
[1] LC_COLLATE=German_Germany.1252 LC_CTYPE=German_Germany.1252
[3] LC_MONETARY=German_Germany.1252 LC_NUMERIC=C
[5] LC_TIME=German_Germany.1252
回答1:
You have set the digits option too low:
options(digits=2)
seq(from = 1, to = 1.1, by = 0.01)
#[1] 1.0 1.0 1.0 1.0 1.0 1.1 1.1 1.1 1.1 1.1 1.1
options(digits=7)
seq(from = 1, to = 1.1, by = 0.01)
#[1] 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10
来源：https://stackoverflow.com/questions/35994327/r-seq-function-produces-wrong-results