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 <[EMAIL PROTECTED]> 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? > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > -- 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 ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
