Fitting a curve to data
And, oddly enough :-), integrate.xy does pretty much exactly what I suggested. Thanks for providing that reference I would be interested in seeing how the original poster's data works out using integrate.xy as opposed to simply calculating x*y By the way, since the original data were 'percent of total volume' over each hour of the day, how could the integral NOT be 100%? Carl
Gabor Grothendieck wrote:
There is an integrate.xy in sfsmic. Limitations discussed there. On Tue, Jul 1, 2008 at 6:27 PM, stephen sefick <ssefick at gmail.com> wrote:
I would like to know the answer to this question now that I know what we are getting at. integrate() looks like it is the right thing, but it has to use a function- I would like to know how to just integrate the area under a curve with just an input of x and y coordinates. Stephen On Tue, Jul 1, 2008 at 5:22 PM, Carl Witthoft <carl at witthoft.com> wrote:
I think the previous answer (to use lm() ) is not necessarily the best option. Since what you want is the definite integral (area under the curve), you can just use one of the existing definite integration tools (sorry, I don't recall the names because I don't use them). If you want to get a "smoothed" curve to remove errors in your data points, I'd recommend fitting a spline and integrating under that.