[R] using subset() in data frame

[Robert Walters]

Greg Snow wrote:
> Look carefully at the output and commands below.
>  
> The first level of porosity is "macro " (notice the space at the 
> end) but you are asking for "macro" (without the space).  Computers are 
> very literal, so "macro " is not equal to "macro".  T

Greg and Chuck,

Thanks for your very generous help. As Greg perceptively noted above, 
there is indeed a space after "macro ". When I went back and changed
porosity == "macro" to "macro " the program ran without a flaw. I think 
this error goes back to the .csv file which I read into R. For some 
reason it's propagating a space after macro that's not visible in the 
file, but R picks up. In future, I'll be careful to note how R expresses 
  variables read from external files.

Sincerely,

Robert Walters