Re: [R] Fitting a curve to data

From: Carl Witthoft <carl_at_witthoft.com>
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
>> 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.
>>>


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