How to subset() from data frame using specific rows

On Tue, 4 Oct 2011, Sarah Goslee wrote:

You asked for pointers, and didn't provide a reproducible example, so 

I

offered a pointer.

Sarah,

   I did not realize that your pointer was to the factor component of 

the

subset() command.

   I think the most parsimonious thing for me to do is to modify the 

database

table with a new column of the full stream name, then re-export and 

re-read

into R.

Hm. I seldom use such approach. In your original request you said you want 
split your data to smaller data frames based on sites 

-----
   I need to create subsets (as data frames) based on sites, but including
all sites on each stream. For example, using the initial site factor shown
------

From what we know it is difficult to say if there is some common feature 

in site variable. If it is organised like

XY-N

you can simply make new variable from first two letters

sites <- substr(chemdata$site,1,2)

then you can split your data frame according to sites

chem.spl <- split(chemdata, sites)

and do anything with your splitted data frames organised in list

Regards
Petr

Thanks,

Rich

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