Simplified syntax

[Michiel Bliemer]

In Ngene Online, we have introduced some new syntax to simplify writing scripts and to generalise some functionality. To illustrate, compare the two scripts below to generate a D-efficient design with uninformative priors whereby only the preference order of the attribute levels is known (to avoid dominant alternatives). The use of parentheses instead of an asterisk in the ;alts property allows more general dominance checks, for example when using ;alts = (car1, car2), (bus1, bus2). Further, utility functions of unlabelled alternatives can now be specified simultaneously. In addition, '.level' is now used after an attribute as a more intuitive indicator to refer to a specific level of a categorical dummy or effects coded variable. For an overview of all features, please refer to the Ngene manual.

Note that the both scripts will run in Ngene Online since it is fully backward compatible.

Ngene Desktop 1.4 syntax

Code: Select all

design
;alts = hotel1*, hotel2*, neither
;rows = 9
;eff = (mnl,d)
;model:
U(hotel1)  = b1[-0.00001]          * price[80,120,160]
           + b2.dummy[0.001|0.002] * stars[3,5,1]
           + b3[-0.000001]         * dist[500,1500,2500],
           + i1                    * price * stars.dummy[5] 
           /
U(hotel2)  = b1                    * price
           + b2.dummy              * stars
           + b3                    * dist[500,1500,2500]
           + i1                    * price * stars.dummy[5] 
           /
U(neither) = b0
$

Ngene Online syntax

Code: Select all

design
;alts = (hotel1, hotel2), neither
;rows = 9
;eff = (mnl,d)
;model:
U(hotel1, hotel2) = b1[-]       * price[80,120,160]
                  + b2.dummy[+] * stars[3,5,1]
                  + b3[-]       * dist[500,1500,2500],
                  + i1          * price * stars.level[5] /
U(neither) = b0
$