MatlabQuery

Language Integrated Query (LINQ) is a Microsoft .NET Framework component that adds SQL-like query expressions to .NET languages. MatlabQuery is a class implementing similar methods for extracting and processing sequences in Matlab. A common interface is presented for numeric arrays, character arrays, cell arrays, structure and object arrays.

Installation

Download MatlabQuery and add the @linq directory to your Matlab path.

Install Steve Eddins's xUnit test framework if you want to run the unit tests.

Examples

query =  linq();

% Numeric array
numbers = randi(10,1,20);
% Sort and keep elements with values < 5
s = query(numbers).sort.takeWhile(@(x) x < 5).toArray;
% Transform and keep first value > 100, if it exists
s = query(numbers).select(@(x) x^2).firstOrDefault(@(x) x >= 100);

% Cell array
words = {'aPPLE', 'BlUeBeRrY', 'cHeRry'};
s = query(words).select(@(x) struct('Upper',upper(x),'Lower',lower(x))).toArray;

% Create a struct array with two fields with numeric values
structs = query(9:-1:0).select(@(x,i) struct('a',x,'b',i)).toArray;
% Return the struct where fields match
s = query(structs).where(@(x) x.a==x.b).toArray

Implemented query operators

Work is in progress to implement all the standard LINQ operators.

Aggregration

LINQ	Matlab
Aggregrate
Average
Count	count	Count # of elements in sequence
Max
Min
Sum

Concatenation

LINQ	Matlab
Concat	concat	Concatenate sequences

Conversion

LINQ	Matlab
AsEnumerable
Cast
OfType	ofType	Filter the elements of a sequence based on a type
ToArray	toArray	Create an array from a sequence
ToDictionary	toDictionary	Create a dictionary from a sequence
ToList	toList	Create a cell array from a sequence

Element

LINQ	Matlab
DefaultIfEmpty
ElementAt	elementAt	Return element at a given index in a sequence
ElementAtOrDefault
First	first	Return first element of sequence
FirstOrDefault	firstOrDefault	Return first element of sequence, or default
Last	last	Return last element of sequence
LastOrDefault	lastOrDefault	Return last element of sequence, or default
Single
SingleOrDefault

Equality

LINQ	Matlab
sequenceEqual

Generation

LINQ	Matlab
Empty	empty	Empty sequence
Range
Repeat

Join

LINQ	Matlab
GroupJoin
Join	join	Inner join based on matching keys extracted from the elements

Ordering

LINQ	Matlab
OrderBy
OrderByDescending
ThenBy
ThenByDescending
	randomize	Randomize sequence order (w/ or w/out replacement)
Reverse	reverse	Reverse sequence order
	sort	Sort sequence
	shuffle	Randomly ermute sequence order

Partition

LINQ	Matlab
Skip	skip	Skip elements from a sequence yielding the remainder
SkipWhile	skipWhile	Skip elements satisfying condition, yielding the remainder
Take	take	Take elements from a sequence skipping the remainder
TakeWhile	takeWhile	Take elements satisfying condition, skipping the remainder

Projection

LINQ	Matlab
Select	select	Evaluate function for each sequence element
SelectMany	selectMany	One-to-many element projection over a sequence

Quantifiers

LINQ	Matlab
All	all	Check if all elements of a sequence satisfy a condition
Any	any	Check if any element of a sequence satisfies a condition
Contains	contains	Check if a sequence contains a given element

Restriction

LINQ	Matlab
Where	where	Yield elements where the predicate function returns true

Set

LINQ	Matlab
Distinct	distinct	Yield unique sequence
Except
Intersect
Union

Contributions

Please feel free to fork and contribute!