nlparci() resid length

The documentation for nlparci() says the following:

"The confidence interval calculation is valid for systems where the length of resid exceeds the length of beta and J has full column rank."

When fitting multiple curves simultaneously, does "length of resid" mean length(resid(:)) or length(resid)? For instance, if I have two curves of 4 data points each, does nlparci consider "length of resid" to be 8 or 4?

Answer 1

[Star Strider]

If you have two curves of 4 data points each, the length of resid is 4, since each curve will create 1 residual value of each data point.

The point is that the number of data points (as reflected by resid) must exceed the number of estimated parameters, beta, in order for the parameters to be estimated uniquely and for the confidence intervals to have any meaningful interpretation.