Displaying 2 results from an estimated 2 matches for "para0".
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2009 Oct 22
1
Automatization of non-linear regression
...of severity vs time")
>
> getInitial(
+ severity ~ SSlogis(time, alpha, xmid, scale),
+ data = data1
+ )
alpha xmid scale
2.212468 12.506960 4.572391
>
>
> ## Using the initial parameters above,
> ## fit the data with a logistic curve.
> para0.st <- c(
+ alpha=2.212,
+ beta=12.507/4.572, # beta in our model is xmid/scale
+ gamma=1/4.572 # gamma (or r) is 1/scale
+ )
>
> fit0 <- nls(
+ severity~alpha/(1+exp(beta-gamma*time)),
+ data1,
+ start=para0.st,
+ trace=T
+ )
0.16...
2009 Dec 18
2
NLS-Weibull-ERROR
...gt; df <- data.frame(conc, vel)
> df
conc vel
1 0.077 1
2 0.328 2
3 0.882 3
4 1.195 4
5 1.884 5
6 3.577 6
7 6.549 7
8 13.000 8
9 33.690 9
10 52.220 10
11 90.140 11
12 166.050 12
13 233.620 13
14 346.890 14
> plot(df$vel, df$conc)
> para0.st <- c(K=450,
+ alpha=0.054,beta=3.398 )
> fit0 <- nls(
+ conc~ K-(K*exp(-(vel/alpha)^beta)), df, start= para0.st,trace=T)
Error in nlsModel(formula, mf, start, wts) :
singular gradient matrix at initial parameter estimates
I will be highly thankful if some one can please...