Mdcheck

Purpose

Missing Data Checker and infiller.

Synopsis

[flag,missmap,infilled] = mdcheck(data,options)

Description

This function checks for missing data and infills it using a PCA model if desired. The input is the data to be checked data as either a double array or a dataset object. Optional input options is a structure containing options for how the function is to run (see below).

Outputs are the fraction of missing data flag, a map of the locations of the missing data as an unint8 variable missmap, and the data with the missing values filled in infilled. Depending on the plots option, a plot of the missing data may also be output.

Options

• options = a structure array with the following fields:

• frac_ssq: [{0.95}] desired fraction between 0 and 1 of variance to be captured by the PCA model,

• max_pcs: [{5}] maximum number of PCs in the model, if 0, then it uses the mean,

• meancenter: ['no' | {'yes'}], tells whether to use mean centering in the algorithm,

• recalcmean: ['no' | {'yes'}], recalculate mean center after each cycle of replacement (may improve results for small matricies),

• display: [{'off'} | 'on'], governs level of display,

• tolerance: [{1e-6 100}] convergence criteria, the first element is the minimum change and the second is the maximum number of iterations,

• max_missing: [{0.4}] maximum fraction of missing data with which MDCHECK will operate, and

• toomuch: [{'error'} | 'exclude'] what action should be taken if too much missing data is found. 'error' exit with error message, 'exclude' will exclude elements (rows/columns/slabs/etc) which contain too much missing data from the data before replacement. 'exclude' requires a dataset object as input for (data),

• algorithm: [ {'svd'} | 'nipals' ] specified the missing data algorithm to use, NIPALS typically used for large amounts of missing data or large multi-way arrays.

Note: MDCHECK captures up to options.frac_ssq of the variance using options.max_pcs or fewer PCA components.

The default options can be retreived using: options = mdcheck('options');.

See Also

parafac, pca