I am an undergraduate student in Isik University, in Istanbul/TURKEY. For my term project, I am studying on the relationship between the prices and market shares of 3 automobile models. I need to find estimates for the parameters so that I can continue my study. I found about your MNP package application on detergent and Japan-election data.
I have found about R, just a week ago. I am totally a stranger to the package, but I am desperate to learn how to implement it. I have installed MNP, after installing the R, but I could not form the correct prompt line to fit my data to Multinomial Probit model (MNP). My problem is as follows: I am studying on the relationship between the prices and market shares of 3 automobile models. I want to find estimates for the model parameters, which MNP finds. I consider three primary automobiles corresponding to the same segment; FIAT-Grande Punto, CITROEN-Clio 3 and VW-Polo. The data I have is 12-months prices for each automobile and their market shares at these months (PricePunto, PriceClio, PricePolo, MarketSharePunto, MarketShareClio, MarketSharePolo). By looking at the examples on detergent-choices and Japanese election applications available with the MNP package, I figured something like;
resX <- mnp(cbind(MarketSharePunto, MarketShareClio, MarketSharePolo) ~ 1,
choiceX= list(PPunto=PricePunto, PClio=PriceClio, PPolo=PricePolo), CXnames = "price", data = rowdata, verbose = TRUE) or
resX <- mnp(cbind(MarketSharePunto, MarketShareClio, MarketSharePolo) ~
PricePunto + PriceClio + PricePolo, data=rowdata, verbose=TRUE) But these two lines do not fit the model to my data; gives errors that I even cannot understand. I could not find the details on MNP function. If I can work this out, I will apply it to another dataset, which involves different automobiles for a longer period of time. If anyone can help me on this, I would be very pleased. Thank you! Ozlem Ipekci (I attached the dataset incase)
PricePunto PriceClio PricePolo MarketSharePunto MarketShareClio MarketSharePolo 23250.0 23900.0 23700 0.007665314 0.009979841 0.009730967 23477.0 24590.0 23250.0 0.007336273 0.006573795 0.006862301 25220.0 25410.0 35350.0 0.00478962 0.007396629 0.001667273 26330.0 26440.0 25360.0 0.003884524 0.005164651 0.00304582 26980.0 27070.0 26240.0 0.004984724 0.003617945 0.005828911 26980.0 25070.0 26490.0 0.004000873 0.007128828 0.004510075 26980.0 25600.0 26490.0 0.006639356 0.006215567 0.003531572 24480.0 25600.0 26490.0 0.008695082 0.005873281 0.002690554 24480.0 25600.0 26640.0 0.004983711 0.005372052 0.005307329 25750 26100 25850 0.002806006 0.004626119 0.005232823 25760.0 26100.0 25850.0 0.004473623 0.003892633 0.003311643 24760.0 24850.0 25850.0 0.007923077 0.006730769 0.003692308
______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.