
Hi,
I'm using the function "mlogit" from the package "mlogit" in order to make a multinomial model, with random and nested effect*. But, currently, even a basic model as

> mlogit(c ~ lma + poids , MC, shape = "long", alt.var = "N")
Erreur dans drop(.Call("La_dgesv", a, as.matrix(b), tol, PACKAGE = "base")) :
  sous-programme Lapack dgesv : le système est exactement singulier

which is the same thing than
Error in drop(.Call("La_dgesv", a, as.matrix(b), tol, PACKAGE = "base")) :
"Lapack routine dgesv: system is exactly singular"

I didn't find any explanations on the web ...

my data look like this

> head(MC)
  male pop lma poids ventre dos date mom   c      N
1    1   2    4.9  3.03      4     3      1    1        no  SS_cache
2    1   2    4.9  3.03      4     3      1    1        no        explo
3    1   2    4.9  3.03      4     3      1    1        no     thermo
4    1   2    4.9  3.03      4     3      1    1        no        immo
5    1   2    4.9  3.03      4     3      1    1        no        stress
6    1   2    4.9  3.03      4     3      1    2       yes   SS_cache

somes data of the Examples (in ?mlogit) look like mine

> head(TravelMode)
  individual  mode choice wait vcost travel gcost income size avincome     time
1          1   air     no   69    59    100    70    3.5    1       35 2.816667
2          1 train     no   34    31    372    71    3.5    1        0 6.766667
3          1   bus     no   35    25    417    70    3.5    1        0 7.533333
4          1   car    yes    0    10    180    30    3.5    1        0 3.000000
5          2   air     no   64    58     68    68    3.0    2       30 2.200000
6          2 train     no   44    31    354    84    3.0    2        0 6.633333
   timeair
1 2.816667
2 0.000000
3 0.000000
4 0.000000
5 2.200000
6 0.000000

and 
> mlogit(choice ~ time + timeair , TravelMode, shape = "long", alt.var = "mode")

Call:
mlogit(formula = choice ~ time + timeair, data = TravelMode,     shape = "long", alt.var = "mode", method = "nr", print.level = 0)

Coefficients:
alttrain    altbus    altcar      time   timeair
 -3.6776   -4.2339   -4.5232   -0.5963   -2.7048

work prefectly

so, I don't understant any thing, ...
Is anybody understand why this function didn't work on my data ?

MANY THANKS


hugo mathé hubertEmail : hugomh@hotmail.fr

PS: * if anybody know how to consider interaction between 2 nested factors, I'm interested ...
(it is "a:b in (A:B)" if a is nested in A and b nested in B ?)
 		 	   		  
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