An alternative to your approach is to pass your data to the approxfun or splinefun functions and then use the integrate function on the result.
On Mon, Aug 24, 2015 at 3:10 AM, CarstenH <cah...@gmx.de> wrote: > Hi all > > I need to calculate the area under a curve (integral) for the following data > pairs: > > Depth SOC > 22.5 0.143 > 28.5 0.165 > 34.5 0.131 > 37.5 0.134 > 40.5 0.138 > 43.5 0.107 > 46.5 0.132 > 49.5 0.175 > 52.5 0.087 > 55.5 0.117 > 58.5 0.126 > 61.5 0.13 > 64.5 0.122 > 67.5 0.161 > 71.5 0.144 > 76.5 0.146 > 82.5 0.156 > 94.5 0.132 > > (Table name is P) > > After reading the data set I assiged the collumns by: > > /x <- (P$Depth) > y <- (P$SOC) > / > > and decided to make a ploynominal function (3rd order): > > /fitP <- lm( y~poly(x,3,raw=TRUE) )/ > > At the next step I failed. I can plot point and function but am not able to > integrate the curve between e.g. depths 20 and 80. > > If I try: > / > integrand <-function(fitP1) > predict(y) > integrate(integrand, lower = 25, upper = 80)/ > > the "Conosle" opend with the message: "Source unavailable or out of sync" > and > / > function(fitP1) > predict(y) > / > ) > > > Would be great if somebody could help! > > Thanks > > Carsten > > > > -- > View this message in context: > http://r.789695.n4.nabble.com/Calculate-the-area-under-a-curve-tp4711418.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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. -- Gregory (Greg) L. Snow Ph.D. 538...@gmail.com ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
