library(mlbench)
library(nnet)
library(kernlab)
library(e1071)
library(earth)
library(caret)

7.2

set.seed(200)
trainingData <- mlbench.friedman1(200, sd=1)
trainingData$x <- data.frame(trainingData$x)
featurePlot(trainingData$x, trainingData$y)

testData <- mlbench.friedman1(5000, sd=1)
testData$x <- data.frame(testData$x)
knnModel <- train(x=trainingData$x, 
                  y=trainingData$y, 
                  method="knn",
                  preProc=c("center", "scale"),
                  tuneLength=10)
knnModel
## k-Nearest Neighbors 
## 
## 200 samples
##  10 predictor
## 
## Pre-processing: centered (10), scaled (10) 
## Resampling: Bootstrapped (25 reps) 
## Summary of sample sizes: 200, 200, 200, 200, 200, 200, ... 
## Resampling results across tuning parameters:
## 
##   k   RMSE      Rsquared   MAE     
##    5  3.466085  0.5121775  2.816838
##    7  3.349428  0.5452823  2.727410
##    9  3.264276  0.5785990  2.660026
##   11  3.214216  0.6024244  2.603767
##   13  3.196510  0.6176570  2.591935
##   15  3.184173  0.6305506  2.577482
##   17  3.183130  0.6425367  2.567787
##   19  3.198752  0.6483184  2.592683
##   21  3.188993  0.6611428  2.588787
##   23  3.200458  0.6638353  2.604529
## 
## RMSE was used to select the optimal model using the smallest value.
## The final value used for the model was k = 17.
knnPred <- predict(knnModel, newdata=testData$x)
postResample(pred=knnPred, obs=testData$y)
##      RMSE  Rsquared       MAE 
## 3.2040595 0.6819919 2.5683461

SVM model

svmRTuned <- train(trainingData$x, trainingData$y,
                   method="svmRadial",
                   preProc=c("center", "scale"),
                   tuneLength=14,
                   trControl=trainControl(method="cv"))
svmRTuned
## Support Vector Machines with Radial Basis Function Kernel 
## 
## 200 samples
##  10 predictor
## 
## Pre-processing: centered (10), scaled (10) 
## Resampling: Cross-Validated (10 fold) 
## Summary of sample sizes: 180, 180, 180, 180, 180, 180, ... 
## Resampling results across tuning parameters:
## 
##   C        RMSE      Rsquared   MAE     
##      0.25  2.505383  0.8031869  1.999381
##      0.50  2.290725  0.8103140  1.829703
##      1.00  2.105086  0.8302040  1.677851
##      2.00  2.014620  0.8418576  1.598814
##      4.00  1.965196  0.8491165  1.567327
##      8.00  1.927649  0.8538945  1.542267
##     16.00  1.924262  0.8545293  1.539275
##     32.00  1.924262  0.8545293  1.539275
##     64.00  1.924262  0.8545293  1.539275
##    128.00  1.924262  0.8545293  1.539275
##    256.00  1.924262  0.8545293  1.539275
##    512.00  1.924262  0.8545293  1.539275
##   1024.00  1.924262  0.8545293  1.539275
##   2048.00  1.924262  0.8545293  1.539275
## 
## Tuning parameter 'sigma' was held constant at a value of 0.06802164
## RMSE was used to select the optimal model using the smallest value.
## The final values used for the model were sigma = 0.06802164 and C = 16.
svmRTuned$finalModel
## Support Vector Machine object of class "ksvm" 
## 
## SV type: eps-svr  (regression) 
##  parameter : epsilon = 0.1  cost C = 16 
## 
## Gaussian Radial Basis kernel function. 
##  Hyperparameter : sigma =  0.0680216365076835 
## 
## Number of Support Vectors : 152 
## 
## Objective Function Value : -66.0924 
## Training error : 0.008551
svmPred <- predict(svmRTuned$finalModel, newdata=testData$x)
postResample(pred=svmPred, obs=testData$y)
##     RMSE Rsquared      MAE 
## 7.156075 0.654429 6.169075

MARS

marsFit <- earth(trainingData$x, trainingData$y)
marsFit
## Selected 12 of 18 terms, and 6 of 10 predictors
## Termination condition: Reached nk 21
## Importance: X1, X4, X2, X5, X3, X6, X7-unused, X8-unused, X9-unused, ...
## Number of terms at each degree of interaction: 1 11 (additive model)
## GCV 2.540556    RSS 397.9654    GRSq 0.8968524    RSq 0.9183982
summary(marsFit)
## Call: earth(x=trainingData$x, y=trainingData$y)
## 
##                coefficients
## (Intercept)       18.451984
## h(0.621722-X1)   -11.074396
## h(0.601063-X2)   -10.744225
## h(X3-0.281766)    20.607853
## h(0.447442-X3)    17.880232
## h(X3-0.447442)   -23.282007
## h(X3-0.636458)    15.150350
## h(0.734892-X4)   -10.027487
## h(X4-0.734892)     9.092045
## h(0.850094-X5)    -4.723407
## h(X5-0.850094)    10.832932
## h(X6-0.361791)    -1.956821
## 
## Selected 12 of 18 terms, and 6 of 10 predictors
## Termination condition: Reached nk 21
## Importance: X1, X4, X2, X5, X3, X6, X7-unused, X8-unused, X9-unused, ...
## Number of terms at each degree of interaction: 1 11 (additive model)
## GCV 2.540556    RSS 397.9654    GRSq 0.8968524    RSq 0.9183982
marsGrid <- expand.grid(.degree=1:2, .nprune=2:38)
marsTuned <- train(trainingData$x, trainingData$y,
                   method="earth",
                   tuneGrid=marsGrid,
                   trControl=trainControl(method="cv"))
marsTuned
## Multivariate Adaptive Regression Spline 
## 
## 200 samples
##  10 predictor
## 
## No pre-processing
## Resampling: Cross-Validated (10 fold) 
## Summary of sample sizes: 180, 180, 180, 180, 180, 180, ... 
## Resampling results across tuning parameters:
## 
##   degree  nprune  RMSE      Rsquared   MAE      
##   1        2      4.555815  0.2211499  3.7894920
##   1        3      3.926474  0.3967924  3.1774338
##   1        4      2.590871  0.7259766  2.0669237
##   1        5      2.294241  0.7891189  1.8337749
##   1        6      2.199933  0.8070077  1.7339981
##   1        7      1.742343  0.8732965  1.3795558
##   1        8      1.666015  0.8845896  1.2982794
##   1        9      1.642477  0.8883691  1.2818259
##   1       10      1.648030  0.8895147  1.2904522
##   1       11      1.617092  0.8944590  1.2649496
##   1       12      1.588637  0.8989528  1.2362045
##   1       13      1.616912  0.8958467  1.2653165
##   1       14      1.617859  0.8959075  1.2598825
##   1       15      1.626588  0.8945949  1.2766998
##   1       16      1.626588  0.8945949  1.2766998
##   1       17      1.626588  0.8945949  1.2766998
##   1       18      1.626588  0.8945949  1.2766998
##   1       19      1.626588  0.8945949  1.2766998
##   1       20      1.626588  0.8945949  1.2766998
##   1       21      1.626588  0.8945949  1.2766998
##   1       22      1.626588  0.8945949  1.2766998
##   1       23      1.626588  0.8945949  1.2766998
##   1       24      1.626588  0.8945949  1.2766998
##   1       25      1.626588  0.8945949  1.2766998
##   1       26      1.626588  0.8945949  1.2766998
##   1       27      1.626588  0.8945949  1.2766998
##   1       28      1.626588  0.8945949  1.2766998
##   1       29      1.626588  0.8945949  1.2766998
##   1       30      1.626588  0.8945949  1.2766998
##   1       31      1.626588  0.8945949  1.2766998
##   1       32      1.626588  0.8945949  1.2766998
##   1       33      1.626588  0.8945949  1.2766998
##   1       34      1.626588  0.8945949  1.2766998
##   1       35      1.626588  0.8945949  1.2766998
##   1       36      1.626588  0.8945949  1.2766998
##   1       37      1.626588  0.8945949  1.2766998
##   1       38      1.626588  0.8945949  1.2766998
##   2        2      4.555815  0.2211499  3.7894920
##   2        3      3.926474  0.3967924  3.1774338
##   2        4      2.590871  0.7259766  2.0669237
##   2        5      2.294241  0.7891189  1.8337749
##   2        6      2.246301  0.7992542  1.8222167
##   2        7      1.753824  0.8708046  1.3826524
##   2        8      1.633425  0.8903708  1.2489141
##   2        9      1.466904  0.9112713  1.1203186
##   2       10      1.324280  0.9278383  1.0547093
##   2       11      1.292964  0.9324603  1.0267734
##   2       12      1.228052  0.9379272  0.9722978
##   2       13      1.217714  0.9392455  0.9649610
##   2       14      1.209324  0.9396066  0.9701953
##   2       15      1.228813  0.9386482  0.9870788
##   2       16      1.217098  0.9392339  0.9809606
##   2       17      1.233891  0.9378794  0.9877503
##   2       18      1.233891  0.9378794  0.9877503
##   2       19      1.233891  0.9378794  0.9877503
##   2       20      1.233891  0.9378794  0.9877503
##   2       21      1.233891  0.9378794  0.9877503
##   2       22      1.233891  0.9378794  0.9877503
##   2       23      1.233891  0.9378794  0.9877503
##   2       24      1.233891  0.9378794  0.9877503
##   2       25      1.233891  0.9378794  0.9877503
##   2       26      1.233891  0.9378794  0.9877503
##   2       27      1.233891  0.9378794  0.9877503
##   2       28      1.233891  0.9378794  0.9877503
##   2       29      1.233891  0.9378794  0.9877503
##   2       30      1.233891  0.9378794  0.9877503
##   2       31      1.233891  0.9378794  0.9877503
##   2       32      1.233891  0.9378794  0.9877503
##   2       33      1.233891  0.9378794  0.9877503
##   2       34      1.233891  0.9378794  0.9877503
##   2       35      1.233891  0.9378794  0.9877503
##   2       36      1.233891  0.9378794  0.9877503
##   2       37      1.233891  0.9378794  0.9877503
##   2       38      1.233891  0.9378794  0.9877503
## 
## RMSE was used to select the optimal model using the smallest value.
## The final values used for the model were nprune = 14 and degree = 2.
marsPred <- predict(marsTuned, newdata=testData$x)
postResample(pred=marsPred, obs=testData$y)
##      RMSE  Rsquared       MAE 
## 1.1722635 0.9448890 0.9324923

The MARS model has the highest Rsquared, at 0.94.

varImp(marsTuned)
## earth variable importance
## 
##    Overall
## X1  100.00
## X4   75.24
## X2   48.74
## X5   15.53
## X3    0.00

MARS selects the informative predictors, X1-X5.


7.5

library(AppliedPredictiveModeling)
data("ChemicalManufacturingProcess")
X <- ChemicalManufacturingProcess[2:58]
y <- ChemicalManufacturingProcess[1]
sum(is.na(X))
## [1] 106
prep <- preProcess(X, method=c("knnImpute"))
prep
## Created from 152 samples and 57 variables
## 
## Pre-processing:
##   - centered (57)
##   - ignored (0)
##   - 5 nearest neighbor imputation (57)
##   - scaled (57)

Impute missing values.

X_imputed <- predict(prep, X)
sum(is.na(X_imputed))
## [1] 0
sample <- sample(c(TRUE, FALSE), nrow(X_imputed), replace=TRUE, prob=c(0.7,0.3))
X_imputed_train <- X_imputed[sample, ]
X_imputed_test <- X_imputed[!sample, ]

y_train <- y[sample, ]
y_test <- y[!sample, ]
  1. Neural network
nnetAvgFit <- nnet(X_imputed_train, y_train,
                size=5,
                decay=0.01,
                repeats=5,
                linout=TRUE,
                trace=FALSE,
                maxit=500,
                MaxNWts=5*(ncol(X_imputed_train)+1)+5+1)
tooHigh <- findCorrelation(cor(X_imputed_train), cutoff=0.75)
trainXnnet <- X_imputed_train[, -tooHigh]
testXnnet <- X_imputed_test[, -tooHigh]
nnetGrid <- expand.grid(.decay=c(0,0.01,0.1),
                        .size=c(1:10),
                        .bag=FALSE)
nnetTune <- train(trainXnnet, y_train,
                  method="avNNet",
                  tuneGrid=nnetGrid,
                  trControl = trainControl(method="cv", number=10),
                  preProc = c("center", "scale"),
                  linout=TRUE,
                  trace=FALSE,
                  MaxNWts=2 * (ncol(trainXnnet)+1) + 2 +1,
                  maxit = 500)
nnetPred <- predict(nnetTune, newdata=testXnnet)
postResample(pred=nnetPred, obs=y_test)
##      RMSE  Rsquared       MAE 
## 1.9434967 0.2432922 1.2256910

MARS

marsGrid1 <- expand.grid(.degree=1:2, .nprune=2:38)
marsTuned1 <- train(trainXnnet, y_train,
                   method="earth",
                   tuneGrid=marsGrid1,
                   trControl=trainControl(method="cv"))
marsPred1 <- predict(marsTuned1, newdata=testXnnet)
postResample(pred=marsPred1, obs=y_test)
##      RMSE  Rsquared       MAE 
## 1.2172127 0.5250973 0.9503113

SVM

svmRTuned1 <- train(trainXnnet, y_train,
                   method="svmRadial",
                   preProc=c("center", "scale"),
                   tuneLength=14,
                   trControl=trainControl(method="cv"))
svmPred1 <- predict(svmRTuned1$finalModel, newdata=testXnnet)
postResample(pred=svmPred1, obs=y_test)
##      RMSE  Rsquared       MAE 
## 1.1990532 0.5070212 0.9435136

KNN

knnModel1 <- train(x=trainXnnet, 
                  y=y_train, 
                  method="knn",
                  preProc=c("center", "scale"),
                  tuneLength=10)
## Warning in preProcess.default(thresh = 0.95, k = 5, freqCut = 19, uniqueCut =
## 10, : These variables have zero variances: BiologicalMaterial07

## Warning in preProcess.default(thresh = 0.95, k = 5, freqCut = 19, uniqueCut =
## 10, : These variables have zero variances: BiologicalMaterial07

## Warning in preProcess.default(thresh = 0.95, k = 5, freqCut = 19, uniqueCut =
## 10, : These variables have zero variances: BiologicalMaterial07

## Warning in preProcess.default(thresh = 0.95, k = 5, freqCut = 19, uniqueCut =
## 10, : These variables have zero variances: BiologicalMaterial07

## Warning in preProcess.default(thresh = 0.95, k = 5, freqCut = 19, uniqueCut =
## 10, : These variables have zero variances: BiologicalMaterial07

## Warning in preProcess.default(thresh = 0.95, k = 5, freqCut = 19, uniqueCut =
## 10, : These variables have zero variances: BiologicalMaterial07

## Warning in preProcess.default(thresh = 0.95, k = 5, freqCut = 19, uniqueCut =
## 10, : These variables have zero variances: BiologicalMaterial07

## Warning in preProcess.default(thresh = 0.95, k = 5, freqCut = 19, uniqueCut =
## 10, : These variables have zero variances: BiologicalMaterial07

## Warning in preProcess.default(thresh = 0.95, k = 5, freqCut = 19, uniqueCut =
## 10, : These variables have zero variances: BiologicalMaterial07

## Warning in preProcess.default(thresh = 0.95, k = 5, freqCut = 19, uniqueCut =
## 10, : These variables have zero variances: BiologicalMaterial07
knnPred1 <- predict(knnModel1, newdata=testXnnet)
postResample(pred=knnPred1, obs=y_test)
##      RMSE  Rsquared       MAE 
## 1.3707688 0.3149447 1.0517262

This model had “zero variance” warnings for one of the predictors, BiologicalMaterial07. Maybe the Rsquared would have been better without it. The MARS model has the best Rsquared, at 0.545.

caret::varImp(marsTuned1)
## earth variable importance
## 
##                        Overall
## ManufacturingProcess36  100.00
## ManufacturingProcess17   51.27
## BiologicalMaterial03      0.00
## ManufacturingProcess28    0.00

The ManufacturingProcess predictors are definitely more important than the BiologicalMaterial predictors.

summary(marsTuned1)
## Call: earth(x=data.frame[120,36], y=c(42.44,43.57,4...), keepxy=TRUE, degree=1,
##             nprune=5)
## 
##                                     coefficients
## (Intercept)                            41.046398
## h(0.658575-BiologicalMaterial03)       -0.758838
## h(ManufacturingProcess17- -1.23678)    -0.856594
## h(ManufacturingProcess28-0.763612)     14.037712
## h(0.488487-ManufacturingProcess36)      0.777073
## 
## Selected 5 of 22 terms, and 4 of 36 predictors (nprune=5)
## Termination condition: RSq changed by less than 0.001 at 22 terms
## Importance: ManufacturingProcess36, ManufacturingProcess17, ...
## Number of terms at each degree of interaction: 1 4 (additive model)
## GCV 1.613195    RSS 165.6348    GRSq 0.5701742    RSq 0.6260233
tops <- c("ManufacturingProcess36","ManufacturingProcess17","ManufacturingProcess28",       
          "BiologicalMaterial03", "ManufacturingProcess37")

cors <- c(cor(testXnnet$ManufacturingProcess36, marsPred1),
          cor(testXnnet$ManufacturingProcess17, marsPred1),
          cor(testXnnet$ManufacturingProcess28, marsPred1),
          cor(testXnnet$BiologicalMaterial03, marsPred1),
          cor(testXnnet$ManufacturingProcess37, marsPred1))
data.frame(predictor=tops, response_correlation=cors)
##                predictor response_correlation
## 1 ManufacturingProcess36           -0.7687756
## 2 ManufacturingProcess17           -0.4682771
## 3 ManufacturingProcess28            0.3728255
## 4   BiologicalMaterial03            0.6032868
## 5 ManufacturingProcess37           -0.1204466

There is only one BiologicalMaterial predictor in the top 5 most important predictors for this MARS model. It has a strong positive correlation with the Yield. Of the four remaining predictors, three of them have negative correlation with the yield.