[R] Odd behaviour of R

[Hiroto Miyoshi]

Dear R-users

I need your help. I am agonised by the odd behaviour of R
described below

In the following program, data.frame "work" contains no rows,
when Pb set to 0.3 and 0.7

data<-read.csv("output.csv",header=TRUE)
for(N in c(20,40,80,160,320,640,1280)){
   for(Pb in seq(0.1,0.9,0.1)){
     work<-data[((data$N==N) & (data$Pb==Pb)),]
     print(work)    
   }
 }

That is, when Pb set to 0.3 and 0.7,
print(work) prints out the message "[1] N        Pb       a        
b        c        d    outcomeA outcomeB <0 rows> (or 0-length row.names)"

However, data does exist when Pb is 0.3 or 0.7. And
when line "work<-data[((data$N==N) & (data$Pb==Pb)),]"
is placed outside the "for" loops after Pb is manually set to 0.3,
print(work) successfully prints out the appropriate data.
Namely,

> N<-20
> Pb<-0.3
>      work<-data[((data$N==N) & (data$Pb==Pb)),]
> work
    N  Pb a b c  d outcomeA outcomeB
22 20 0.3 6 0 0 14    FALSE    FALSE
23 20 0.3 5 1 0 14    FALSE    FALSE
24 20 0.3 5 1 1 13    FALSE    FALSE
...................................................................

Why is this happen?
I am using R version 2.3.0.
Any help is greatly appreciated.

Thank you.


------------------------
Hiroto Miyoshi
h_m_ at po.harenet.ne.jp