I'm doing a regression analysis considering fixed effects using plm() from package plm. I have selected the twoways method to account for both time and individual effects. However, after runing the below code I keep receiving this message:
Error in pdata.frame(data, index) :
variable id does not exist (individual index)
Here the code:
pdata <- DATABASE[,c(2:4,13:21)]
pdata$id <- group_indices(pdata,ISO3.p,Productcode)
coutnin <- dcast.data.table(pdata,ISO3.p+Productcode~.,value.var = "id")
setcolorder(pdata,neworder=c("id","Year"))
pdata <- pdata.frame(pdata,index=c("id","Year"))
reg <- plm(pdata,diff(TV,1) ~ diff(RERcp,1)+diff(GDPR.p,1)-diff(GDPR.r,1), effect="twoways", model="within", index = c("id","Year"))
Please mind that pdata structure shows that there are multiple levels in the id variable which is in numeric form, I tried initially to use a string type variable but I keep receiving the same outcome:
Classes ‘data.table’ and 'data.frame': 1211800 obs. of 13 variables:
$ id : int 4835 6050 13158 15247 17164 18401 19564 23553 24895 27541 ...
$ Year : int 1996 1996 1996 1996 1996 1996 1996 1996 1996 1996 ...
$ Productcode: chr "101" "101" "101" "101" ...
$ ISO3.p : Factor w/ 171 levels "ABW","AFG","AGO",..: 8 9 20 22 27 28 29 34 37 40 ...
$ e : num 0.245 -0.238 1.624 0.693 0.31 ...
$ RERcp : num -0.14073 -0.16277 1.01262 0.03908 -0.00243 ...
$ RERpp : num -0.1712 NA NA NA -0.0952 ...
$ RER_GVC : num -3.44 NaN NA NA NaN ...
$ GDPR.p : num 27.5 26.6 23.5 20.3 27.8 ...
$ GDPR.r : num 30.4 30.4 30.4 30.4 30.4 ...
$ GVCPos : num 0.141 0.141 0.141 0.141 0.141 ...
$ GVCPar : num 0.436 0.436 0.436 0.436 0.436 ...
$ TV : num 17.1 17.1 17.1 17.1 17.1 ...
- attr(*, ".internal.selfref")=<externalptr>
When I convert the data.table into a pdata.frame I do not receive any warning, it happens only after I run the plm function. From running View(table(index(pdata), useNA = "ifany")) it displays no value larger than 1, therefore I assume I have no duplicates obs in my data.
Try to put the data argument at the second place in the plm statement. In case pdata has been converted to a pdata.frame already, leave out the index argument in the plm statement, i.e., try this:
reg <- plm(diff(TV,1) ~ diff(RERcp,1)+diff(GDPR.p,1)-diff(GDPR.r,1), data = pdata, effect = "twoways", model = "within")