Programming

Summary of Matrix and Array Functions

This section summarizes the principal functions used in creating and handling matrices. Most of these functions work on multidimensional arrays as well.

Functions to Create a Matrix

Function	Description
[a,b] or [a;b]	Create a matrix from specified elements, or concatenate matrices together.
accumarray	Construct a matrix using accumulation.
blkdiag	Construct a block diagonal matrix.
cat	Concatenate matrices along the specified dimension.
diag	Create a diagonal matrix from a vector.
horzcat	Concatenate matrices horizontally.
magic	Create a square matrix with rows, columns, and diagonals that add up to the same number.
ones	Create a matrix of all ones.
rand	Create a matrix of uniformly distributed random numbers.
repmat	Create a new matrix by replicating or tiling another.
vertcat	Concatenate two or more matrices vertically.
zeros	Create a matrix of all zeros.

Functions to Modify the Shape of a Matrix

Function	Description
ctranspose	Flip a matrix about the main diagonal and replace each element with its complex conjugate.
flipdim	Flip a matrix along the specified dimension.
fliplr	Flip a matrix about a vertical axis.
flipud	Flip a matrix about a horizontal axis.
reshape	Change the dimensions of a matrix.
rot90	Rotate a matrix by 90 degrees.
transpose	Flip a matrix about the main diagonal.

Functions to Find the Structure or Shape of a Matrix

Function	Description
isempty	Return true for 0-by-0 or 0-by-n matrices.
isscalar	Return true for 1-by-1 matrices.
issparse	Return true for sparse matrices.
isvector	Return true for 1-by-n matrices.
length	Return the length of a vector.
ndims	Return the number of dimensions in a matrix.
numel	Return the number of elements in a matrix.
size	Return the size of each dimension.

Functions to Determine Data Type

Function	Description
iscell	Return true if the matrix is a cell array.
ischar	Return true if matrix elements are characters or strings.
isfloat	Determine if input is a floating point array.
isinteger	Determine if input is an integer array.
islogical	Return true if matrix elements are logicals.
isnumeric	Return true if matrix elements are numeric.
isreal	Return true if matrix elements are real numbers.
isstruct	Return true if matrix elements are MATLAB structures.

Functions to Sort and Shift Matrix Elements

Function	Description
circshift	Circularly shift matrix contents.
issorted	Return true if the matrix elements are sorted.
sort	Sort elements in ascending or descending order.
sortrows	Sort rows in ascending order.

Functions That Work on Diagonals of a Matrix

Function	Description
blkdiag	Construct a block diagonal matrix.
diag	Return the diagonals of a matrix.
trace	Compute the sum of the elements on the main diagonal.
tril	Return the lower triangular part of a matrix.
triu	Return the upper triangular part of a matrix.

Functions to Change the Indexing Style

Function	Description
ind2sub	Convert a linear index to a row-column index.
sub2ind	Convert a row-column index to a linear index.

Functions for Working with Multidimensional Arrays

Function	Description
cat	Concatenate arrays.
circshift	Shift array circularly.
ipermute	Inverse permute array dimensions.
ndgrid	Generate arrays for n-dimensional functions and interpolation.
ndims	Return the number of array dimensions.
permute	Permute array dimensions.
shiftdim	Shift array dimensions.
squeeze	Remove singleton dimensions.

Multidimensional Structure Arrays

Data Types

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