# Nesting

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### Yuri Groeneveld

Jan 17, 2023, 9:50:58 AMJan 17
to Biogeme
Dear Michel,

I am estimating a nested destination-mode choice model but the mu is lower than 1, 0.46. I've read on this google group that thats no correct and the nesting is done wrong. Yet I can't find the error. Thus, is it incorrect or is it possible in some cases?

for i in PC4_limburg:
nests.append((MU_zone, [int(f'{i}1'), int(f'{i}2'), int(f'{i}3')]))

Here I create my nests. For every zone, I nest the car, pt and bike with the same mu for every zone. Because the nesting is the same for every zone.

Yuri

### Bierlaire Michel

Jan 17, 2023, 9:53:31 AMJan 17
to yagroe...@gmail.com, Bierlaire Michel, Biogeme
Indeed, MU must be greater or equal to one.
It is actually a good iea to constrain the lower bound of the MU to 1.
I suggest to use a different mu for each nest.

Also, try different nesting structures. Instead of nesting per destination, try to nest per mode.

If nothing works, consider cross-nested logit.

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### Yuri Groeneveld

Jan 18, 2023, 10:15:33 AMJan 18
to Biogeme
Another question,

I can't find clearly how to calculate the probability for each nest and within the nest, only the derivative.
Could you elaborate?

Thanks,
Yuri

Op dinsdag 17 januari 2023 om 15:53:31 UTC+1 schreef michel.b...@epfl.ch:

### Yuri Groeneveld

Jan 19, 2023, 2:27:51 AMJan 19
to Biogeme
Thanks.

When I try nesting with the different modes, car and pt are 1 when constrained to 1 and bike is 1.07.
When I try a CNL the run time takes more than 72 hours. The run time of a mode NL is already over 5 hours.

My alternatives are zones in a province in The Netherlands and I want to apply that mu to other zones in The Netherlands thus I can't have specific mu's for specific zones.

With kind regards,
Yuri

Op dinsdag 17 januari 2023 om 15:53:31 UTC+1 schreef michel.b...@epfl.ch:
Indeed, MU must be greater or equal to one.