[R] correlation

[stephen sefick]

This may be incorrect, but couldn't you just assign a number to the
ratings 1:4 and then scatterplot them agianst N (x-axis).  Or you may
want to plot boxplots of N by water quality ratings.  If these are
water quality ratings derived from aquatic macroinvertebrates and you
have access to the actual count information (reguardless of taxanomic
level) you may want to consider some ordination techniques to see if
there is an ecological gradient underlying your taxa information.
hope this helps and good luck

Stephen

On Thu, Oct 16, 2008 at 9:05 AM, kdebusk <kdebusk at gmail.com> wrote:
> What test do I use to determine if there is a correlation between a
> discrete variable and a continuous variable?
>
> For example - I have water quality ratings for streams (excellent,
> good, fair, poor) and a corresponding nitrogen concentration for each
> rating. I want to know if the the ratings correlate with the
> concentration of nitrogen in the stream.
>
> Help?
>
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-- 
Stephen Sefick
Research Scientist
Southeastern Natural Sciences Academy

Let's not spend our time and resources thinking about things that are
so little or so large that all they really do for us is puff us up and
make us feel like gods.  We are mammals, and have not exhausted the
annoying little problems of being mammals.

								-K. Mullis