From: Carl Witthoft <carl_at_witthoft.com>

Date: Tue, 01 Jul 2008 19:07:35 -0400

>> 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
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*>> 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.
*

*>>>
*

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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. Received on Tue 01 Jul 2008 - 23:10:11 GMT

Date: Tue, 01 Jul 2008 19:07:35 -0400

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

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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. Received on Tue 01 Jul 2008 - 23:10:11 GMT

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