I am trying to fit a logistic price demand curve like so: ods select none;
proc nlmixed data=TrainingData;
bounds L > 100, Sd1 > 0, Parameter1 > 0, k > 0, var2 >= 0;
parms L = 101, Sd1 = 0.5, Intercept = 1.0, Parameter1 = 0.001, k = 2, pa1=18, b1 =0;
Parameter1 = pa1 + b1;
Y = L / -k * exp(Intercept + Parameter1 * Price);
model Demand ~ normal(Y, Sd1);
random b1 ~ normal(0, var2) subject = ProductId;
ods output
Parameters = Parameters
FitStatistics = ModelFit
;
run;
ods select all; This code is just a starting point! I played around with some parameters in Excel and found some OK-ish ones, which I provided as starting parameters. Unfortunately, the algorithm does not change the provided parameters when I inspect dataset Parameters (created using Parameters = Parameters). I doubt I chose the optimal parameters - so I would expect the parameters in the dataset Parameters to be adjusted. Is there something wrong with the above, which prevents the parameters from being changed? Thanks!
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