search for: macroinvertebr

...t the previous two are surely related to the last (this ratio has been suggested to show nutrient limitation, but there is the possibility that the concentrations of the two constituents are high enough where the ratio is not that meaningful). Or maybe when particulate organic carbon is related to macroinvertebrate density with scales as divergent as 1mg/L to 1000insects/m^2 . The good parts about base graphics are that you can do anything you want to even if it is wrong, but I'm responsible for my actions or assumptions. ggplot is a wonderful piece of software and most of its defaults are wonderful,...

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?