[R] Problem while predicting in regression trees

[Bert Gunter]

It seems that the data that you used for prediction contained a level
"Hospitals" for the sector factor that did not appear in the training
data (or maybe it's the other way round). Check this.

Cheers,
Bert


Bert Gunter

"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Sun, May 8, 2016 at 4:14 PM, Muhammad Bilal
<Muhammad2.Bilal at live.uwe.ac.uk> wrote:
> Hi All,
>
> I have the following script, that raises error at the last command. I am new to R and require some clarification on what is going wrong.
>
> #Creating the training and testing data sets
> splitFlag <- sample.split(pfi_v3, SplitRatio = 0.7)
> trainPFI <- subset(pfi_v3, splitFlag==TRUE)
> testPFI <- subset(pfi_v3, splitFlag==FALSE)
>
>
> #Structure of the trainPFI data frame
>> str(trainPFI)
> *******
> 'data.frame': 491 obs. of  16 variables:
>  $ project_id             : int  1 2 3 6 7 9 10 12 13 14 ...
>  $ project_lat            : num  51.4 51.5 52.2 51.9 52.5 ...
>  $ project_lon            : num  -0.642 -1.85 0.08 -0.401 -1.888 ...
>  $ sector                 : Factor w/ 9 levels "Defense","Hospitals",..: 4 4 4 6 6 6 6 6 6 6 ...
>  $ contract_type          : chr  "Turnkey" "Turnkey" "Turnkey" "Turnkey" ...
>  $ project_duration       : int  1826 3652 121 730 730 790 522 819 998 372 ...
>  $ project_delay          : int  -323 0 -60 0 0 0 -91 0 0 7 ...
>  $ capital_value          : num  6.7 5.8 21.8 24.2 40.7 10.7 70 24.5 60.5 78 ...
>  $ project_delay_pct      : num  -17.7 0 -49.6 0 0 0 -17.4 0 0 1.9 ...
>  $ delay_type             : Ord.factor w/ 9 levels "7 months early & beyond"<..: 1 5 3 5 5 5 2 5 5 6 ...
>
> library(caret)
> library(e1071)
>
> set.seed(100)
>
> tr.control <- trainControl(method="cv", number=10)
> cp.grid <- expand.grid(.cp = (0:10)*0.001)
>
> #Fitting the model using regression tree
> tr_m <- train(project_delay ~ project_lon + project_lat + project_duration + sector + contract_type + capital_value, data = trainPFI, method="rpart", trControl=tr.control, tuneGrid = cp.grid)
>
> tr_m
>
> CART
> 491 samples
> 15 predictor
> No pre-processing
> Resampling: Cross-Validated (10 fold)
> Summary of sample sizes: 443, 442, 441, 442, 441, 442, ...
> Resampling results across tuning parameters:
>   cp     RMSE      Rsquared
>   0.000  441.1524  0.5417064
>   0.001  439.6319  0.5451104
>   0.002  437.4039  0.5487203
>   0.003  432.3675  0.5566661
>   0.004  434.2138  0.5519964
>   0.005  431.6635  0.5577771
>   0.006  436.6163  0.5474135
>   0.007  440.5473  0.5407240
>   0.008  441.0876  0.5399614
>   0.009  441.5715  0.5401718
>   0.010  441.1401  0.5407121
> RMSE was used to select the optimal model using  the smallest value.
> The final value used for the model was cp = 0.005.
>
> #Fetching the best tree
> best_tree <- tr_m$finalModel
>
> Alright, all the aforementioned commands worked fine.
>
> Except the subsequent command raises error, when the developed model is used to make predictions:
> best_tree_pred <- predict(best_tree, newdata = testPFI)
> Error in eval(expr, envir, enclos) : object 'sectorHospitals' not found
>
> Can someone guide me what to do to resolve this issue.
>
> Any help will be highly appreciated.
>
> Many Thanks and
>
> Kind Regards
>
> --
> Muhammad Bilal
> Research Fellow and Doctoral Researcher,
> Bristol Enterprise, Research, and Innovation Centre (BERIC),
> University of the West of England (UWE),
> Frenchay Campus,
> Bristol,
> BS16 1QY
>
> muhammad2.bilal at live.uwe.ac.uk<mailto:olugbenga2.akinade at live.uwe.ac.uk>
>
>
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>
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