Hi Bryan,
Division by 2 is correct, comes from trapezoid calculation.
The modulo line is a funny way of producing c (2 : n, 1)
Best,
Claudia
Am Mon, 18 Mar 2013 15:00:06 -0400
schrieb Bryan Hanson <han...@depauw.edu>:
> If you type DrawChromatogram you can see the method used to calculate
> the peak area. Looks to me like you could easily hack it if you
> wanted. The relevant part about peak areas is this:
>
> for (j in 1:n) {
> k <- (j%%n) + 1
> x[j] <- peakTime[j] * peakIntensity[k] - peakTime[k] *
> peakIntensity[j]
> }
> peakArea[i] <- abs(sum(x)/2)
>
> which looks pretty standard to me, though I'm not clear right off the
> top of my head why they are dividing by 2. You can always contact
> the maintainer.
>
> Bryan
>
> On Mar 18, 2013, at 1:34 PM, Christopher Beaver
> <christopher.bea...@gmail.com> wrote:
>
> > Hello!
> >
> > I am having an issue with the OrgMassSpecR package. I run my HPLC
> > using a DAD detector. My raw data is exported form chemstation as
> > a csv file. I then upload the csv into Rstudio no problem. Using
> > the DrawChromatogram function, I get a nice chromatogram, and my
> > retention time, peak area, and apex intensity values are given as
> > well.
> >
> > The problem comes with the peak area value given. The peak area is
> > much smaller than a value that would make sense. My peak area
> > value is actually less than my apex intensity value. Is this
> > because I am using a DAD detector rather than an MS? If so, is
> > there a simply way to edit the peak area equation so that it will
> > also work with absorbance values?
> >
> > Any help is greatly appreciated.
> >
> > Thanks for your time.
> >
> > Chris Beaver
> >
> > [[alternative HTML version deleted]]
> >
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--
Claudia Beleites
Spectroscopy/Imaging
Institute of Photonic Technology
Albert-Einstein-Str. 9
07745 Jena
Germany
email: claudia.belei...@ipht-jena.de
phone: +49 3641 206-133
fax: +49 2641 206-399
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