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+---
+language: Matlab
+contributors:
+    - ["mendozao", "http://github.com/mendozao"]
+    - ["jamesscottbrown", "http://jamesscottbrown.com"]
+
+---
+
+MATLAB stands for MATrix LABoratory. It is a powerful numerical computing language commonly used in engineering and mathematics.
+
+If you have any feedback please feel free to reach me at
+[@the_ozzinator](https://twitter.com/the_ozzinator), or
+[osvaldo.t.mendoza@gmail.com](mailto:osvaldo.t.mendoza@gmail.com).
+
+```matlab
+% Comments start with a percent sign.
+
+%{
+Multi line comments look
+something
+like
+this
+%}
+
+% commands can span multiple lines, using '...':
+ a = 1 + 2 + ...
+ + 4
+
+% commands can be passed to the operating system
+!ping google.com
+
+who % Displays all variables in memory
+whos % Displays all variables in memory, with their types
+clear % Erases all your variables from memory
+clear('A') % Erases a particular variable
+openvar('A') % Open variable in variable editor
+
+clc % Erases the writing on your Command Window
+diary % Toggle writing Command Window text to file
+ctrl-c % Abort current computation
+
+edit('myfunction.m') % Open function/script in editor
+type('myfunction.m') % Print the source of function/script to Command Window
+
+profile on 	% turns on the code profiler
+profile off 	% turns off the code profiler
+profile viewer 	% Open profiler
+
+help command 	% Displays documentation for command in Command Window
+doc command 	% Displays documentation for command in Help Window
+lookfor command % Searches for command in the first commented line of all functions
+lookfor command -all % searches for command in all functions
+
+
+% Output formatting
+format short 	% 4 decimals in a floating number
+format long 	% 15 decimals
+format bank 	% only two digits after decimal point - for financial calculations
+fprintf('text') % print "text" to the screen
+disp('text') 	% print "text" to the screen
+
+% Variables & Expressions
+myVariable = 4 	% Notice Workspace pane shows newly created variable
+myVariable = 4; % Semi colon suppresses output to the Command Window
+4 + 6  		% ans = 10
+8 * myVariable 	% ans = 32
+2 ^ 3 		% ans = 8
+a = 2; b = 3;
+c = exp(a)*sin(pi/2) % c = 7.3891
+
+% Calling functions can be done in either of two ways:
+% Standard function syntax:
+load('myFile.mat', 'y') % arguments within parantheses, spererated by commas
+% Command syntax:
+load myFile.mat y 	% no parentheses, and spaces instead of commas
+% Note the lack of quote marks in command form: inputs are always passed as
+% literal text - cannot pass variable values. Also, can't receive output:
+[V,D] = eig(A);  % this has no equivalent in command form
+[~,D] = eig(A);  % if you only want D and not V
+
+
+
+% Logicals
+1 > 5 % ans = 0
+10 >= 10 % ans = 1
+3 ~= 4 % Not equal to -> ans = 1
+3 == 3 % equal to -> ans = 1
+3 > 1 && 4 > 1 % AND -> ans = 1
+3 > 1 || 4 > 1 % OR -> ans = 1
+~1 % NOT -> ans = 0
+
+% Logicals can be applied to matrices:
+A > 5
+% for each element, if condition is true, that element is 1 in returned matrix
+A( A > 5 )
+% returns a vector containing the elements in A for which condition is true
+
+% Strings
+a = 'MyString'
+length(a) % ans = 8
+a(2) % ans = y
+[a,a] % ans = MyStringMyString
+
+
+% Cells
+a = {'one', 'two', 'three'}
+a(1) % ans = 'one' - returns a cell
+char(a(1)) % ans = one - returns a string
+
+% Structures
+A.b = {'one','two'};
+A.c = [1 2];
+A.d.e = false;
+
+% Vectors
+x = [4 32 53 7 1]
+x(2) % ans = 32, indices in Matlab start 1, not 0
+x(2:3) % ans = 32 53
+x(2:end) % ans = 32 53 7 1
+
+x = [4; 32; 53; 7; 1] % Column vector
+
+x = [1:10] % x = 1 2 3 4 5 6 7 8 9 10
+
+% Matrices
+A = [1 2 3; 4 5 6; 7 8 9]
+% Rows are separated by a semicolon; elements are separated with space or comma
+% A =
+
+%     1     2     3
+%     4     5     6
+%     7     8     9
+
+A(2,3) % ans = 6, A(row, column)
+A(6) % ans = 8
+% (implicitly concatenates columns into vector, then indexes into that)
+
+
+A(2,3) = 42 % Update row 2 col 3 with 42
+% A =
+
+%     1     2     3
+%     4     5     42
+%     7     8     9
+
+A(2:3,2:3) % Creates a new matrix from the old one
+%ans =
+
+%     5     42
+%     8     9
+
+A(:,1) % All rows in column 1
+%ans =
+
+%     1
+%     4
+%     7
+
+A(1,:) % All columns in row 1
+%ans =
+
+%     1     2     3
+
+[A ; A] % Concatenation of matrices (vertically)
+%ans =
+
+%     1     2     3
+%     4     5    42
+%     7     8     9
+%     1     2     3
+%     4     5    42
+%     7     8     9
+
+% this is the same as
+vertcat(A,A);
+
+
+[A , A] % Concatenation of matrices (horizontally)
+
+%ans =
+
+%     1     2     3     1     2     3
+%     4     5    42     4     5    42
+%     7     8     9     7     8     9
+
+% this is the same as
+horzcat(A,A);
+
+
+A(:, [3 1 2]) % Rearrange the columns of original matrix
+%ans =
+
+%     3     1     2
+%    42     4     5
+%     9     7     8
+
+size(A) % ans = 3 3
+
+A(1, :) =[] % Delete the first row of the matrix
+A(:, 1) =[] % Delete the first column of the matrix
+
+transpose(A) % Transpose the matrix, which is the same as:
+A one
+ctranspose(A) % Hermitian transpose the matrix
+% (the transpose, followed by taking complex conjugate of each element)
+
+
+
+
+% Element by Element Arithmetic vs. Matrix Arithmetic
+% On their own, the arithmetic operators act on whole matrices. When preceded
+% by a period, they act on each element instead. For example:
+A * B % Matrix multiplication
+A .* B % Multiple each element in A by its corresponding element in B
+
+% There are several pairs of functions, where one acts on each element, and
+% the other (whose name ends in m) acts on the whole matrix.
+exp(A) % exponentiate each element
+expm(A) % calculate the matrix exponential
+sqrt(A) % take the square root of each element
+sqrtm(A) %  find the matrix whose square is A
+
+
+% Plotting
+x = 0:.10:2*pi; % Creates a vector that starts at 0 and ends at 2*pi with increments of .1
+y = sin(x);
+plot(x,y)
+xlabel('x axis')
+ylabel('y axis')
+title('Plot of y = sin(x)')
+axis([0 2*pi -1 1]) % x range from 0 to 2*pi, y range from -1 to 1
+
+plot(x,y1,'-',x,y2,'--',x,y3,':') % For multiple functions on one plot
+legend('Line 1 label', 'Line 2 label') % Label curves with a legend
+
+% Alternative method to plot multiple functions in one plot.
+% while 'hold' is on, commands add to existing graph rather than replacing it
+plot(x, y)
+hold on
+plot(x, z)
+hold off
+
+loglog(x, y) % A log-log plot
+semilogx(x, y) % A plot with logarithmic x-axis
+semilogy(x, y) % A plot with logarithmic y-axis
+
+fplot (@(x) x^2, [2,5]) % plot the function x^2 from x=2 to x=5
+
+grid on % Show grid; turn off with 'grid off'
+axis square % Makes the current axes region square
+axis equal % Set aspect ratio so data units are the same in every direction
+
+scatter(x, y); % Scatter-plot
+hist(x); % Histogram
+
+z = sin(x);
+plot3(x,y,z); % 3D line plot
+
+pcolor(A) % Heat-map of matrix: plot as grid of rectangles, coloured by value
+contour(A) % Contour plot of matrix
+mesh(A) % Plot as a mesh surface
+
+h = figure	% Create new figure object, with handle f
+figure(h) % Makes the figure corresponding to handle h the current figure
+close(h) % close figure with handle h
+close all % close all open figure windows
+close % close current figure window
+
+shg % bring an existing graphics window forward, or create new one if needed
+clf clear % clear current figure window, and reset most figure properties
+
+% Properties can be set and changed through a figure handle.
+% You can save a handle to a figure when you create it.
+% The function gcf returns a handle to the current figure
+h = plot(x, y); % you can save a handle to a figure when you create it
+set(h, 'Color', 'r')
+% 'y' yellow; 'm' magenta, 'c' cyan, 'r' red, 'g' green, 'b' blue, 'w' white, 'k' black
+set(h, 'LineStyle', '--')
+ % '--' is solid line, '---' dashed, ':' dotted, '-.' dash-dot, 'none' is no line
+get(h, 'LineStyle')
+
+
+% The function gca returns a handle to the axes for the current figure
+set(gca, 'XDir', 'reverse'); % reverse the direction of the x-axis
+
+% To create a figure that contains several axes in tiled positions, use subplot
+subplot(2,3,1); % select the first position in a 2-by-3 grid of subplots
+plot(x1); title('First Plot') % plot something in this position
+subplot(2,3,2); % select second position in the grid
+plot(x2); title('Second Plot') % plot something there
+
+
+% To use functions or scripts, they must be on your path or current directory
+path % display current path
+addpath /path/to/dir % add to path
+rmpath /path/to/dir % remove from path
+cd /path/to/move/into % change directory
+
+
+% Variables can be saved to .mat files
+save('myFileName.mat') % Save the variables in your Workspace
+load('myFileName.mat') % Load saved variables into Workspace
+
+% M-file Scripts
+% A script file is an external file that contains a sequence of statements.
+% They let you avoid repeatedly typing the same code in the Command Window
+% Have .m extensions
+
+% M-file Functions
+% Like scripts, and have the same .m extension
+% But can accept input arguments and return an output
+% Also, they have their own workspace (ie. different variable scope).
+% Function name should match file name (so save this example as double_input.m).
+% 'help double_input.m' returns the comments under line beginning function
+function output = double_input(x)
+	%double_input(x) returns twice the value of x
+	output = 2*x;
+end
+double_input(6) % ans = 12
+
+
+% You can also have subfunctions and nested functions.
+% Subfunctions are in the same file as the primary function, and can only be
+% called by functions in the file. Nested functions are defined within another
+% functions, and have access to both its workspace and their own workspace.
+
+% If you want to create a function without creating a new file you can use an
+% anonymous function. Useful when quickly defining a function to pass to
+% another function (eg. plot with fplot, evaluate an indefinite integral
+% with quad, find roots with fzero, or find minimum with fminsearch).
+% Example that returns the square of it's input, assigned to to the handle sqr:
+sqr = @(x) x.^2;
+sqr(10) % ans = 100
+doc function_handle % find out more
+
+% User input
+a = input('Enter the value: ')
+
+% Stops execution of file and gives control to the keyboard: user can examine
+% or change variables. Type 'return' to continue execution, or 'dbquit' to exit
+keyboard
+
+% Reading in data (also xlsread/importdata/imread for excel/CSV/image files)
+fopen(filename)
+
+% Output
+disp(a) % Print out the value of variable a
+disp('Hello World') % Print out a string
+fprintf % Print to Command Window with more control
+
+% Conditional statements (the parentheses are optional, but good style)
+if (a > 15)
+	disp('Greater than 15')
+elseif (a == 23)
+	disp('a is 23')
+else
+	disp('neither condition met')
+end
+
+% Looping
+% NB. looping over elements of a vector/matrix is slow!
+% Where possible, use functions that act on whole vector/matrix at once
+for k = 1:5
+	disp(k)
+end
+
+k = 0;
+while (k < 5)
+	k = k + 1;
+end
+
+% Timing code execution: 'toc' prints the time since 'tic' was called
+tic
+A = rand(1000);
+A*A*A*A*A*A*A;
+toc
+
+% Connecting to a MySQL Database
+dbname = 'database_name';
+username = 'root';
+password = 'root';
+driver = 'com.mysql.jdbc.Driver';
+dburl = ['jdbc:mysql://localhost:8889/' dbname];
+javaclasspath('mysql-connector-java-5.1.xx-bin.jar'); %xx depends on version, download available at http://dev.mysql.com/downloads/connector/j/
+conn = database(dbname, username, password, driver, dburl);
+sql = ['SELECT * from table_name where id = 22'] % Example sql statement
+a = fetch(conn, sql) %a will contain your data
+
+
+% Common math functions
+sin(x)
+cos(x)
+tan(x)
+asin(x)
+acos(x)
+atan(x)
+exp(x)
+sqrt(x)
+log(x)
+log10(x)
+abs(x)
+min(x)
+max(x)
+ceil(x)
+floor(x)
+round(x)
+rem(x)
+rand % Uniformly distributed pseudorandom numbers
+randi % Uniformly distributed pseudorandom integers
+randn % Normally distributed pseudorandom numbers
+
+% Common constants
+pi
+NaN
+inf
+
+% Solving matrix equations (if no solution, returns a least squares solution)
+% The \ and / operators are equivalent to the functions mldivide and mrdivide
+x=A\b % Solves Ax=b. Faster and more numerically accurate than using inv(A)*b.
+x=b/A % Solves xA=b
+
+inv(A) % calculate the inverse matrix
+pinv(A) % calculate the pseudo-inverse
+
+% Common matrix functions
+zeros(m,n) % m x n matrix of 0's
+ones(m,n) % m x n matrix of 1's
+diag(A) % Extracts the diagonal elements of a matrix A
+diag(x) % Construct a matrix with diagonal elements listed in x, and zeroes elsewhere
+eye(m,n) % Identity matrix
+linspace(x1, x2, n) % Return n equally spaced points, with min x1 and max x2
+inv(A) % Inverse of matrix A
+det(A) % Determinant of A
+eig(A) % Eigenvalues and eigenvectors of A
+trace(A) % Trace of matrix - equivalent to sum(diag(A))
+isempty(A) % Tests if array is empty
+all(A) % Tests if all elements are nonzero or true
+any(A) % Tests if any elements are nonzero or true
+isequal(A, B) % Tests equality of two arrays
+numel(A) % Number of elements in matrix
+triu(x) % Returns the upper triangular part of x
+tril(x) % Returns the lower triangular part of x
+cross(A,B) %  Returns the cross product of the vectors A and B
+dot(A,B) % Returns scalar product of two vectors (must have the same length)
+transpose(A) % Returns the transpose of A
+fliplr(A) % Flip matrix left to right
+flipud(A) % Flip matrix up to down
+
+% Matrix Factorisations
+[L, U, P] = lu(A) % LU decomposition: PA = LU,L is lower triangular, U is upper triangular, P is permutation matrix
+[P, D] = eig(A) % eigen-decomposition: AP = PD, P's columns are eigenvectors and D's diagonals are eigenvalues
+[U,S,V] = svd(X) % SVD: XV = US, U and V are unitary matrices, S has non-negative diagonal elements in decreasing order
+
+% Common vector functions
+max     % largest component
+min     % smallest component
+length  % length of a vector
+sort    % sort in ascending order
+sum     % sum of elements
+prod    % product of elements
+mode	% modal value
+median  % median value
+mean    % mean value
+std     % standard deviation
+perms(x) % list all permutations of elements of x
+
+```
+
+## More on Matlab
+
+* The official website [http://http://www.mathworks.com/products/matlab/](http://www.mathworks.com/products/matlab/)
+* The official MATLAB Answers forum: [http://www.mathworks.com/matlabcentral/answers/](http://www.mathworks.com/matlabcentral/answers/)
+