[R] Odp: Translate Sine Function in R?

[Petr PIKAL]

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 2Ď€ (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
> 
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> 
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