Sorry, I sent that e-mail too soon. I realize you called "x.seq" just "x" in the data frame.
Yes, this is a great way to fit these data. I think from this that I can probably now work with the related function of the line to get my minimum and maximum values. Thanks for your assistance! Katrina On Fri, Aug 5, 2011 at 4:41 PM, Katrina Bennett <kebenn...@alaska.edu>wrote: > Hi Petr, > Thank you for the response. > > I am not familiar with the nls package. I am interested in obtaining a > function to represent the relationship observed in "dat" over x.seq (days) > so that I can calculate a minimum and maximum of the function. > > In the example below, it seems like you are using a data frame, but I tried > to create the data frame from x.seq and dat: > > dat.df <- data.frame(x.seq, dat) > > However, I got the following error: > > Error in nls(dat ~ SSlogis(x, Asym, xmid, scal), data = dat.df, start = > list(Asym = 90, : > parameters without starting value in 'data': x > > Thank you for your assistance, > > Katrina > > > On Thu, Aug 4, 2011 at 11:14 PM, Petr PIKAL <petr.pi...@precheza.cz>wrote: > >> Hi >> >> Are you sure about sine fit? Seems to me that logistics would be better >> >> fit<-nls(dat ~ SSlogis(x, Asym, xmid,scal), data = dat.df, start = >> list(Asym=90, xmid = 75, scal = -6)) >> plot(dat.df) >> lines(dat.df$x[complete.cases(dat.df)], predict(fit)) >> >> Regards >> Petr >> >> >> >> > >> > Hello, I'm trying to generate a sine wave in R to fit my observations >> using >> > the general formula: >> > >> > y=a*sin(b[x+h*pi)]+k >> > >> > where a = amplitude, b=period, h=phase shift, and k=vertical shift >> > >> > I want to use following translation to bring the sine function up onto >> the >> > y-axis to range from 0-1, and this will place the wave on the x-axis >> from >> > 0-pi/2. >> > >> > y=1/2sin(2[x+ 1/4*pi]) + 1/2 >> > >> > Additionally, I need to spread this along a x-axis that spans 1-153 >> (days). >> > >> > Can anyone help with this? I seem to be able to use the curve function >> fine, >> > but entering the translations doesn't seem to provide an answer. >> > >> > Here is an example of the data set I am trying to 'match' using this >> > function. >> > >> > dat <- >> > >> c(75.44855206,NA,NA,NA,82.70745342,82.5335019,88.56617647,80.00128866,94. >> > 15418227,86.63987539,93.91052952,74.10612245,86.62289562,90. >> > 47961047,NA,NA,82.45320197,72.14371257,NA,71.44104803,72.59742896,68. >> > 36363636,NA,NA,61,NA,NA,71.26502909,NA,85.93333333,84.34248284,79. >> > 00522193,79.64223058,97.2074017,88.43700548,96.40413877,95.13511869,92. >> > 57379057,93.97498475,NA,97.55995131,89 >> .53321146,97.21728545,93.21980198, >> > 77.54054054,95.85392575,86.25684723,97.55325624,80.03950617,NA,91. >> > 34023128,92.42906574,88.59433962,65.77272727,89.63772455,NA,NA,NA,NA,74. >> > 86344239,83.57594937,70.22516556,65.30543319,NA,NA,67.84852294,60. >> > 90909091,54.79303797,NA,52.18735363,33.47003155,NA,41.34693878,24. >> > 5047043,NA,NA,NA,NA,9.944444444,13.6875,NA,11.90267176,84.14285714,3. >> > 781456954,NA,1.432926829,4.26557377,1.823529412,0.444620253,4. >> > >> 711155378,NA,6.320284698,0.581632653,0.144578313,3.666666667,0,0,0,0,0,NA, >> > 0.032947462,0,0,10.54545455,0,NA,0.561007958,0.75,NA,0.048780488,0. >> > 74137931,NA,2.023339318,0,0,0,NA,NA,0.156950673,NA,0.283769634,32. >> > >> 81818182,NA,NA,0,NA,0,0,0,NA,0.212454212,3.120181406,NA,0.011811024,NA,0, >> > >> 0.120430108,5.928571429,1.75,0.679292929,0.97,NA,0,NA,NA,1,0.38547486,NA, >> > 1.460732984,0.007795889,0.05465288,0.004341534) >> > plot(dat/100) >> > par(new=F) >> > x.seq <- seq(100, 0, , 153) >> > y <- ??? #*y = 2 sin 2Ä⬠(x - 1/4)* or y ~ a + c*sin(x+b) >> > >> > However, I can't find a reference for the no place for k. Also, I've >> tried a >> > lot of different iterations, but can't seem to figure out how to do this >> in >> > R. >> > >> > Any thoughts or ideas on this? >> > >> > Thank you, >> > >> > Katrina >> > >> > [[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. >> >> [[alternative HTML version deleted]]
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