I want to find the value which makes the following function predict the observations contained in the following dataset.
require(mosaic)
d=data.frame(t=c(41.5,44,42.77,47), y=c(230,76.4/60,3.4,1))
fitModel(y~(-(47-t)*I/(35-t)*(1+exp((42.77-t)*I))),
data=d,start=list(I=3.1,t=47))
It seems I am replicating exactly what the example in the function's help says, but yet it reports a rather obscure error message.
Error in qr(.swts * gr) : dims [product 2] does not match the length of object [4]
Any suggestions?
t is your independent variable, it should not be included in the “start” list.
Try:
require(mosaic)
d=data.frame(t=c(41.5, 44, 42.77, 47), y=c(230, 76.4/60, 3.4, 1))
fitModel(y~(-(47-t)*I/(35-t)*(1+exp((42.77-t)*I))),
data=d, start=list(I=3.1))
Using nls() as alternative to fitModel():
nls(y~(-(47-t)*I/(35-t)*(1+exp((42.77-t)*I))),
data=d, start=list(I=3.1))
Nonlinear regression model
model: y ~ (-(47 - t) * I/(35 - t) * (1 + exp((42.77 - t) * I)))
data: d
I
3.432
residual sum-of-squares: 1.126
Number of iterations to convergence: 4
Achieved convergence tolerance: 4.092e-07