Data Preprocessing

This part of the package provides a simple set of preprocessing utilities.

Data Normalization

mapstd(X)

Normalizes each column of X to zero mean and one standard deviation. Output normalized matrix X with extracted column-wise means and standard deviations.

using SALSA

mapstd([0 1; -1 2]) # --> ([0.707107  -0.707107; -0.707107   0.707107], [-0.5  1.5], [0.707107 0.707107])

mapstd(X, mean, std)

Normalizes each column of A to the specified column-wise mean and std. Output normalized matrix X.

using SALSA

mapstd([0 1; -1 2], [-0.5  1.5], [0.707107 0.707107]) # --> [0.707107  -0.707107; -0.707107   0.707107]

Sparse Data Preparation

make_sparse(tuples[, sizes, delim])

Creates SparseMatrixCSC object from matrix of tuples Matrix{ASCIIString} containing index:value pairs. The index and value pair can be separated by delim character, e.g. :. The user can optionally specify final dimensions of the SparseMatrixCSC object as sizes tuple.

Parameters:

• tuples – matrix of tuples Matrix{ASCIIString} containing index:value pairs
• sizes – optional tuple of final dimensions, e.g. (100000,10) (empty by default)
• delim – optional character separating index and value pair in each cell of tuples, default is ”:”

Returns:

SparseMatrixCSC object.

Data Management

DelimitedFile(name, header, delim)

Creates a wrapper around any delimited file which can be passed to low-level routines, for instance pegasos_alg(). DelimitedFile will be processed in the online mode regardless of the online_pass==0 flag passed to low-level routines.

Parameters:

• name – file name
• header – flag indicating if a header is present
• delim – delimiting character