mixed models - R mlogit-Error system is computationally singular: reciprocal condition number -


i using library(mlogit) in r , stuck @ particular data set looks this

 customerid item price calories choice            1  200  1.99      490    no             1  312  4.99      887    no             1  560  5.19      910    no             1  700  4.79      690    no             1  909  4.89      660    no             1 1705  4.00      840    no  

there 187 items in total , 4 customerid(1,2,3 , 4). each customer presented choice set of 187 items selects 1 based on price , calories. price , calories remain same 4 customers.

> str(data) 'data.frame':   748 obs. of  5 variables:  $ customerid: int  1 1 1 1 1 1 1 1 1 1 ...  $ item      : factor w/ 187 levels "200","231","232",..: 1 11 14 15 18 25 33 34 36 39 ...  $ price     : num  1.99 4.99 5.19 4.79 4.89 4 4 4 4 6.21 ...  $ calories  : int  490 887 910 690 660 840 1638 1559 1530 1559 ...  $ choice    : factor w/ 2 levels "no ","yes": 1 1 1 1 1 1 1 1 1 1 ... 

i format data according mlogit command in manner below:-

m<- mlogit.data(data, choice="choice", shape="long", alt.levels=c("200",    "231",    "232",    "240",.....(*all 187 'item' here)*)) 

which gives me this:-

head(m)       customerid item price calories choice 1.200          1  200  1.99      490    no  1.231          1  231  1.19      320    yes 1.232          1  232  1.49      320    no  1.240          1  240  4.79      590    no  1.250          1  250  2.39      490    no  1.253          1  253  4.49      691    no  

my dataset ordered cutomerid , item had read in previous question might cause issue.

i try several formulas none of them runs

tr.ml <- mlogit(choice ~0|price+calories|0,m) error in solve.default(h, g[!fixed]) :    lapack routine dgesv: system singular: u[548,548] = 0 in addition: there 50 or more warnings (use warnings() see first 50) 

the correlation between price , calories 43%

cor(m$price,m$calories) [1] 0.429796 

i tried this:-

tr.ml <- mlogit(choice ~price+calories,m) error in solve.default(h, g[!fixed]) :    system computationally singular: reciprocal condition number = 1.06243e-23 in addition: there 50 or more warnings (use warnings() see first 50) 

can provide thoughts on resolving error? have been @ 2 weeks now.


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