# dims: Dimension of NMF Objects In NMF: Algorithms and Framework for Nonnegative Matrix Factorization (NMF)

## Description

The methods `dim`, `nrow`, `ncol` and `nbasis` return the different dimensions associated with an NMF model.

`dim` returns all dimensions in a length-3 integer vector: the number of row and columns of the estimated target matrix, as well as the factorization rank (i.e. the number of basis components).

`nrow`, `ncol` and `nbasis` provide separate access to each of these dimensions respectively.

## Usage

 ```1 2 3 4 5 6 7``` ``` nbasis(x, ...) ## S4 method for signature 'NMF' dim(x) ## S4 method for signature 'NMFfitXn' dim(x) ```

## Arguments

 `x` an object with suitable `basis` and `coef` methods, such as an object that inherit from `NMF`. `...` extra arguments to allow extension.

## Details

The NMF package does not implement specific functions `nrow` and `ncol`, but rather the S4 method `dim` for objects of class `NMF`. This allows the base methods `nrow` and `ncol` to directly work with such objects, to get the number of rows and columns of the target matrix estimated by an NMF model.

The function `nbasis` is a new S4 generic defined in the package NMF, that returns the number of basis components of an object. Its default method should work for any object, that has a suitable `basis` method defined for its class.

## Value

a single integer value or, for `dim`, a length-3 integer vector, e.g. `c(2000, 30, 3)` for an `NMF` model that fits a 2000 x 30 matrix using 3 basis components.

## Methods

dim

`signature(x = "NMF")`: method for NMF objects for the base generic `dim`. It returns all dimensions in a length-3 integer vector: the number of row and columns of the estimated target matrix, as well as the factorization rank (i.e. the number of basis components).

dim

`signature(x = "NMFfitXn")`: Returns the dimension common to all fits.

Since all fits have the same dimensions, it returns the dimension of the first fit. This method returns `NULL` if the object is empty.

nbasis

`signature(x = "ANY")`: Default method which returns the number of columns of the basis matrix extracted from `x` using a suitable method `basis`, or, if the latter is `NULL`, the value of attributes `'nbasis'`.

For NMF models, this also corresponds to the number of rows in the coefficient matrix.

nbasis

`signature(x = "NMFfitXn")`: Returns the number of basis components common to all fits.

Since all fits have been computed using the same rank, it returns the factorization rank of the first fit. This method returns `NULL` if the object is empty.

NMF documentation built on Aug. 1, 2020, 9:06 a.m.