Scale Columns of a Matrix

x	the matrix to be scaled. Missing values (NAs) are allowed.
center	specifies whether or how to control the value subtracted from each column. Can be a logical value or a vector. If TRUE (the default), the mean of the non-missing data in each column is subtracted from the column. If given as a vector of length ncol(x), this vector is used. That is, center[j] is subtracted from column j. If FALSE, no centering is done.
scale	specifies whether or how to control the value divided into each column to scale it. Can be a logical value or a vector. If TRUE (the default), after centering, each column is divided by the square root of sum-of-squares over n-1, where n is the number of non-missing values. If given as a vector of length ncol(x), column j is divided by scale[j]. If FALSE, no scaling is done.

Details

scale takes as an argument x (matrix) and returns a similar matrix whose columns take elements corresponding to the center (mean), and scale (standard deviation). If center and scale are not specified, the default values are 0 and 1, respectively.

returns a matrix like x with optional centering and scaling.

If scale is TRUE or a vector (that is, not FALSE), this matrix has an attribute scaled:scale containing the vector of values used to scale the columns.
If center is TRUE or a vector (that is, not FALSE), this matrix has an attribute scaled:center containing the vector of values used to center the columns.

A <- matrix(c(1:3,3*(1:3),2^(1:3)), nrow=3) A # [,1] [,2] [,3] # [1,] 1 3 2 # [2,] 2 6 4 # [3,] 3 9 8

# center and scale scale(A) # [,1] [,2] [,3] # [1,] -1 -1 -0.8728716 # [2,] 0 0 -0.2182179 # [3,] 1 1 1.0910895 # attr(,"scaled:center") # [1] 2.000000 6.000000 4.666667 # attr(,"scaled:scale") # [1] 1.00000 3.00000 3.05505

# check column means and variances of centered and scaled matrix apply(scale(A),2,mean) # [1] 0.000000e+000 0.000000e+000 -1.480297e-016 apply(scale(A),2,var) # [1] 1 1 1

# just center scale(A, scale=FALSE) # [,1] [,2] [,3] # [1,] -1 -3 -2.6666667 # [2,] 0 0 -0.6666667 # [3,] 1 3 3.3333333 # attr(,"scaled:center") # [1] 2.000000 6.000000 4.666667

# just scale scale(A, center=FALSE) # [,1] [,2] [,3] # [1,] 0.3779645 0.3779645 0.3086067 # [2,] 0.7559289 0.7559289 0.6172134 # [3,] 1.1338934 1.1338934 1.2344268 # attr(,"scaled:scale") # [1] 2.645751 7.937254 6.480741

# just center by a vector of values scale(A, center=c(1,2,4), scale=FALSE) # [,1] [,2] [,3] # [1,] 0 1 -2 # [2,] 1 4 0 # [3,] 2 7 4 # attr(,"scaled:center") # [1] 1 2 4

# just scale by a vector of values scale(A, center=FALSE, scale=c(1,2,4)) # [,1] [,2] [,3] # [1,] 1 1.5 0.5 # [2,] 2 3.0 1.0 # [3,] 3 4.5 2.0 # attr(,"scaled:scale") # [1] 1 2 4

Description

Usage

Arguments

Details