R help - May 2007 - conditional across frames of a data fram

I'm a newbie, so please forgive me:

I have a data frame that includes two long columns of x and y coordinate
values thusly:
...   ...   ...   x       y  ...   ...
...   ...   ...   115   127 ...  ...
...   ...   ...   120   129 ...   ...
...   ...   ...   0       0   ...   ...
...   ...   ...   135   162 ....   ...
ect...

  i need to ask R tell me how many x-y pairs contain coords that are
non-zero and fall within values that i'm callilng xleft, xright, ybottom and
ytop and fall between certain indicies of the data frame.
i am calling the indexes by referring to numbers i have storied in other
variables.  i am really looking for an efficient way to do this since when i
try to pull the x and y columns out and assign them to their own variables,
the process of asking for the number of non-zeros which have x values such
that xleft <= x <= xright AND ybottom <= y <=ytop, the process
becomes very
convoluted.  how can i ask for more than one conditional at once?
  thanks for any help,
  jason

	[[alternative HTML version deleted]]

Does this do it for you?

sum((df$x >= xleft) & (df$x <= xright) & (df$y >= ybottom)
& (df$y <= ytop))


On 5/11/07, Jason Vytlacil <jason.vytlacil at gmail.com>
wrote:
>  I'm a newbie, so please forgive me:
>
> I have a data frame that includes two long columns of x and y coordinate
> values thusly:
> ...   ...   ...   x       y  ...   ...
> ...   ...   ...   115   127 ...  ...
> ...   ...   ...   120   129 ...   ...
> ...   ...   ...   0       0   ...   ...
> ...   ...   ...   135   162 ....   ...
> ect...
>
>  i need to ask R tell me how many x-y pairs contain coords that are
> non-zero and fall within values that i'm callilng xleft, xright,
ybottom and
> ytop and fall between certain indicies of the data frame.
> i am calling the indexes by referring to numbers i have storied in other
> variables.  i am really looking for an efficient way to do this since when
i
> try to pull the x and y columns out and assign them to their own variables,
> the process of asking for the number of non-zeros which have x values such
> that xleft <= x <= xright AND ybottom <= y <=ytop, the process
becomes very
> convoluted.  how can i ask for more than one conditional at once?
>  thanks for any help,
>  jason
>
>        [[alternative HTML version deleted]]
>
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>

-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?