# normalize

0th

Percentile

##### Normalize the ratings

Provides the generic for normalize/denormalize and a method to normalize/denormalize the ratings in a realRatingMatrix.

Keywords
Manipulation
##### Usage
normalize(x, ...)
"normalize"(x, method="center", row=TRUE)
denormalize(x, ...)
"denormalize"(x, method=NULL, row=NULL,  factors=NULL)
##### Arguments
x
a realRatingMatrix.
method
normalization method. Currently "center" or "Z-score".
row
logical; normalize rows (or the columns)?
factors
a list with the factors to be used for denormalizing (elements are "mean" and "sds"). Usually these are not specified and the values stored in x are used.
...
further arguments (currently unused).
##### Details

Normalization tries to reduce the individual rating bias by row centering the data, i.e., by subtracting from each available rating the mean of the ratings of that user (row). Z-score in addition divides by the standard deviation of the row/column. Normalization can also be done on columns.

Denormalization reverses normalization. It uses the normalization information stored in x unless the user specifies method, row and factors.

##### Value

A normalized realRatingMatrix.

##### Aliases
• normalize
• denormalize
• denormalize,realRatingMatrix-method
• normalize,realRatingMatrix-method
##### Examples
## create a matrix with ratings
m <- matrix(sample(c(NA,0:5),50, replace=TRUE, prob=c(.5,rep(.5/6,6))),
nrow=5, ncol=10, dimnames = list(users=paste('u', 1:5, sep=''),
items=paste('i', 1:10, sep='')))

## do normalization
r <- as(m, "realRatingMatrix")
r_n1 <- normalize(r)
r_n2 <- normalize(r, method="Z-score")

r
r_n1
r_n2

## show normalized data
image(r, main="Raw Data")
image(r_n1, main="Centered")
image(r_n2, main="Z-Score Normalization")

Documentation reproduced from package recommenderlab, version 0.2-1, License: GPL-2

### Community examples

Looks like there are no examples yet.