my first model with biome

[Gabriel Dias]

Dear professor Bierlaire,

I am doing my first model with Biogeme for a stated choice experiment where respondents had to choose between four modes of transport, having the car as the current mode for trips.

I wrote the codes in Biogeme, however, the beta calculations two of the variables are appointed with no values, and with active bound of 1.

Could you help me in finding out what is the problem with the model?

thanks in advance. 

ASC_CAR = Beta('ASC_CAR', 0, None, None, 0)
ASC_BUS = Beta('ASC_BUS', 0, None, None, 0)
ASC_BIKE = Beta('ASC_BIKE', 0, None, None, 0)
ASC_SCOOTER = Beta('ASC_SCOOTER', 0, None, None, 0)

B_TIME = Beta('B_TIME', 0, None, 0, 0)
B_COST = Beta('B_COST', 0, None, 0, 0)
B_INFRA = Beta('B_INFRA', 0, None, 0, 0)
B_TECH = Beta('B_TECH', 0, None, 0, 0)

V_CAR = (
    ASC_CAR +
    B_TIME * CAR_TT +
    B_COST * CAR_CO +
    B_INFRA * CAR_IS +
    B_TECH * CAR_TC
)

V_BUS = (
    ASC_BUS +
    B_TIME * BUS_TT +
    B_COST * BUS_CO +
    B_INFRA * BUS_IS +
    B_TECH * BUS_TC
)

V_SCOOTER = (
    B_TIME * SCOOTER_TT +
    B_COST * SCOOTER_CO +
    B_INFRA * SCOOTER_IS +
    B_TECH * SCOOTER_TC
)

V_BIKE = (
    B_TIME * BIKE_TT +
    B_COST * BIKE_CO +
    B_INFRA * BIKE_IS +
    B_TECH * BIKE_TC
)

[Michel Bierlaire]

I don't know how this variable is defined, but why do you set lower bounds to zero? Set None instead.
If it is still estimated at 0, it means that you have no variability in the data.

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Michel Bierlaire
Transport and Mobility Laboratory
School of Architecture, Civil and Environmental Engineering
EPFL - Ecole Polytechnique Fédérale de Lausanne
http://transp-or.epfl.ch
http://people.epfl.ch/michel.bierlaire