Having a bit of an issue and I don’t quite know where to turn.

I have insect emergence data that fits a Gompertz model quite well.

Example Data

Row │ ED Wasp

│ Float64 Float64

─────┼──────────────────

1 │ 14.375 2.0

2 │ 14.875 1.0

3 │ 15.375 10.0

4 │ 15.5417 11.0

5 │ 15.7083 1.0

6 │ 15.875 9.0

7 │ 16.5417 351.0

8 │ 16.7083 4.0

9 │ 16.875 153.0

10 │ 17.375 36.0

11 │ 17.5417 110.0

12 │ 17.7083 4.0

13 │ 18.375 55.0

14 │ 18.5417 105.0

15 │ 18.7083 1.0

16 │ 19.375 8.0

17 │ 19.5417 41.0

18 │ 19.7083 3.0

19 │ 20.5417 8.0

20 │ 21.5417 5.0

21 │ 21.7083 1.0

22 │ 21.875 1.0

23 │ 22.375 3.0

24 │ 22.5417 5.0

25 │ 24.5417 2.0

I am currently using RCall to determine the coefficients of the Gompertz Model based on the data. The equation R uses is below

`y~a*exp(-b*exp(-c*x)`

where

a is the asymptote

b is displacement along the x axis

c is the growth rate

all is well and good to this point.

the kink comes from a paper i found that uses the SpSS version of the equation

`y~a*exp(-exp(-c*(x-m)))’

where

a is the asymptote

b is an implied 1

c is slope of the growing part of the curve

m is the inflection point or where the growth goes exponetial.

What I would like to do is use the SPSS version without having to purchase and learn how to use SPSS to determine the fit of a line with the data.

I have no idea if any of this makes sense but I am happy to clarify and answer any questions.

Thank you so much

Mike