Hi Instead of RR function
fit<-nls(cum~ exp(-((size/r)^gama))*100, data=PSD, start=c(r=80, gama=2)) you need to use equation for lognormal distribution. You can find it on internet http://en.wikipedia.org/wiki/Log-normal_distribution My math skills are not high enough to present canned solution. Petr From: Zorig Davaanyam [mailto:dzo...@gmail.com] Sent: Saturday, December 21, 2013 12:36 AM To: PIKAL Petr Subject: Re: [R] Fitting particle size analysis data Hi, Thanks for the reply. Do you know how to find the fitted parameters of lognormal distribution? Regards, Zorig On Fri, Dec 20, 2013 at 5:35 AM, PIKAL Petr <petr.pi...@precheza.cz<mailto:petr.pi...@precheza.cz>> wrote: Hi I made a simple spredsheet for PSD using Rosin Rammler equation and I am lazy to transform it to R. However for single purpose you can use nls. Reverse your cumulative values PSD$cum<-cumsum(PSD$ret) plot(PSD$size, PSD$cum) fit<-nls(cum~ exp(-((size/r)^gama))*100, data=PSD, start=c(r=80, gama=2)) summary(fit) Formula: cum ~ exp(-((size/r)^gama)) * 100 Parameters: Estimate Std. Error t value Pr(>|t|) r 88.9664 2.3360 38.09 2.35e-07 *** gama 2.5435 0.2244 11.33 9.36e-05 *** --- Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 Residual standard error: 3.411 on 5 degrees of freedom Number of iterations to convergence: 7 Achieved convergence tolerance: 1.612e-06 lines(PSD$size, predict(fit)) Regards Petr > -----Original Message----- > From: r-help-boun...@r-project.org<mailto:r-help-boun...@r-project.org> > [mailto:r-help-bounces@r-<mailto:r-help-bounces@r-> > project.org<http://project.org>] On Behalf Of Zorig Davaanyam > Sent: Friday, December 20, 2013 2:01 AM > To: r-help@r-project.org<mailto:r-help@r-project.org> > Subject: [R] Fitting particle size analysis data > > Hi all, > > How do you fit a sieve analysis data to a statistical function? > I have many sieve analysis data of crushed rocks and I'd like to find > out which statistical distributions describe the particular particle > size distributions (PSD) the best. So basically I need to find fitted > parameters to statistical distributions (mostly weibull and truncated > lognormal). > Here is an example of particle size (in microns) versus percent weight > retained. > Sieve size Wt% Cumulative passing% > +250 0.1 99.9 > -250+180 2.9 97 > -180+125 9.5 87.5 > -125+90 21.2 66.3 > -90+63 29.4 36.9 > -63+45 26 10.9 > -45 10.9 > > PSD<- > data.frame(size=c(250,180,125,90,63,45,0),retained=c(0.1,2.9,9.5,21.2,2 > 9.4,26,10.9),cumulative=c(99.9,97,87.5,66.3,36.9,10.9,0)) > > The above example is truncated to 350micron and I can't have particles > with minus dimension. Any help will be greatly appreciated. > > Thank you, > > Zorig > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org<mailto: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. [[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.
