normalize
From recommenderlab v0.21
by Michael Hahsler
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 "Zscore".
 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). Zscore 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.
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="Zscore")
r
r_n1
r_n2
## show normalized data
image(r, main="Raw Data")
image(r_n1, main="Centered")
image(r_n2, main="ZScore Normalization")
Community examples
Looks like there are no examples yet.