(This article was first published on

Together with Mateusz Zawisza I have just published a new book in Polish on building predictive models in GNU R. It can be bought at Oficyna Wydawnicza SGH. The book presents complete examples of basic data mining processes.**R snippets**, and kindly contributed to R-bloggers)Although the book is in Polish, sources of all procedures used in it, which are available on my website, can be used without the book. Here is a simplified code from exercise 4.5 presenting neural network bagging:

library

**(**nnet**)**set.seed

**(**1**)**SAMPLE_SIZE

**<-**256X

**<-**seq**(-**2, 2, length.out**=**SAMPLE_SIZE**)**TRUE_Y

**<-**X**^**2**/**2**+**sin**(**4*****X**)**y

**<-**TRUE_Y**+**2*****rnorm**(**SAMPLE_SIZE**)**GetBootstrapPrediction

**<-****function****()****{** bootstrap.indices

**<-**sample**(**SAMPLE_SIZE, replace**=**T**)** bootstrap.sample.y

**<-**y**[**bootstrap.indices**]** bootstrap.sample.x

**<-**X**[**bootstrap.indices**]** bootstrap.model

**<-**nnet**(**bootstrap.sample.y**~**bootstrap.sample.x, lin

**=**T, size**=**4, trace**=****FALSE**, maxit**=**10**^**6**)** return

**(**predict**(**bootstrap.model, data.frame**(**bootstrap.sample.x**=**X**)))****}**

progress.bar

**<-**winProgressBar**(**"Progress in %", "0% done", 0, 1, 0**)**BOOTSTRAP_REPLICATIONS

**<-**1024bootstrap.predictions

**<-**rep**(**0, SAMPLE_SIZE**)****for**

**(**i

**in**1

**:**BOOTSTRAP_REPLICATIONS

**)**

**{**

bootstrap.predictions

**<-**bootstrap.predictions**+** GetBootstrapPrediction

**()** percentage

**<-**i**/**BOOTSTRAP_REPLICATIONS setWinProgressBar

**(**progress.bar, percentage, "Progress in %", sprintf

**(**"%d%% done", round**(**100*****percentage**)))****}**

close

**(**progress.bar**)**plot

**(**X, y,xlim**=**c**(-**2, 2**)**, ylim**=**c**(-**5, 6**))**lines

lines**(**X, TRUE_Y, lwd**=**4**)****(**X, bootstrap.predictions

**/**BOOTSTRAP_REPLICATIONS,

lwd

**=**3, col

**=**3

**)**

It produces the following graph. Circles represent training data, black line is true relationship and green line is prediction from bagging procedure:

To

**leave a comment**for the author, please follow the link and comment on his blog:**R snippets**.R-bloggers.com offers

**daily e-mail updates**about R news and tutorials on topics such as: visualization (ggplot2, Boxplots, maps, animation), programming (RStudio, Sweave, LaTeX, SQL, Eclipse, git, hadoop, Web Scraping) statistics (regression, PCA, time series, trading) and more...