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]] > > > > ______________________________________________ > > R-help@r-project.org mailing list > > 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. > > ______________________________________________ > R-help@r-project.org mailing list > 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. -- 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 ______________________________________________ R-help@r-project.org mailing list 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.