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Added MATLAB as a new language
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Osvaldo Mendoza
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matlab.html.markdown
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matlab.html.markdown
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---
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language: Matlab
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contributors:
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- ["mendozao", "http://github.com/mendozao"]
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---
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Matlab stands for Matrix Laboratory. It is a powerful numerical computing language commonly used in engineering and mathematics.
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If you have any feedback please feel free to reach me at
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[@the_ozzinator](https://twitter.com/the_ozzinator), or
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[osvaldo.t.mendoza@gmail.com](mailto:osvaldo.t.mendoza@gmail.com).
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```Matlab
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% Comments start with a percent sign.
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%{ Multi line comments look
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something
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like
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this %}
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clear % Erases all your variables from memory
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clc % Erases the writing on your Command Window
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who % Displays all variables in memory
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diary % History of session
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ctrl-c % Abort current computation
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help command % Displays documentation for command in Command Window
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lookfor command % Searches for a given command
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% Output formatting
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format short % 4 decimals in a floating number
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format long % 15 decimals
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fprintf
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% Variables & Expressions
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myVariable = 4 % Notice Workspace pane shows newly created variable
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myVariable = 4; % Semi colon suppresses output to the Command Window
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4 + 6 % ans = 10
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8 * myVariable % ans = 32
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a = 2; b = 3;
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c = exp(a)*sin(pi/2) % c = 7.3891
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% Logicals
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1 > 5 % ans = 0
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10 >= 10 % ans = 1
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3 ~= 4 % Not equal to -> ans = 1
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3 == 3 % equal to -> ans = 1
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3 > 1 && 4 > 1 % AND -> ans = 1
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3 > 1 || 4 > 1 % OR -> ans = 1
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~1 % NOT -> ans = 0
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% Strings
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a = 'MyString'
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length(a) % ans = 8
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a(2) % ans = y
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[a,a] % ans = MyStringMyString
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% Cells
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a = {'one', 'two', 'three'}
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a(1) % ans = 'one' - returns a cell
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char(a(1)) % ans = one - returns a string
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% Vectors
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x = [4 32 53 7 1]
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x(2) % ans = 32, indices in Matlab start 1, not 0
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x(2:3) % ans = 32 53
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x(2:end) % ans = 32 53 7 1
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x = [4; 32; 53; 7; 1] % Column vector
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x = [1:10] % x = 1 2 3 4 5 6 7 8 9 10
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% Matrices
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A = [1 2 3; 4 5 6; 7 8 9]
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% Rows are seperated with a semi colon, each element is seperated with space or comma
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% A =
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% 1 2 3
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% 4 5 6
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% 7 8 9
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A(2,3) % ans = 6, A(row, column)
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A(2,3) = 42 % Update row 2 col 3 with 42
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% A =
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% 1 2 3
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% 4 5 42
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% 7 8 9
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A(2:3,2:3) % Creates a new matrix from the old one
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%ans =
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% 5 42
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% 8 9
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A(:,1) % All rows in column 1
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%ans =
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% 1
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% 4
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% 7
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A(1,:) % All columns in row 1
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%ans =
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% 1 2 3
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A(:, [3 1 2]) %Rearrange the columns of original matrix
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%ans =
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% 3 1 2
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% 42 4 5
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% 9 7 8
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A(1, :) =[] %Delete the first row of the matrix
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size(A) % ans = 3 3
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A' % Transpose the matrix
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[A ; A] % Concatenation of matrices
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%ans =
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% 1 2 3
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% 4 5 42
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% 7 8 9
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% 1 2 3
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% 4 5 42
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% 7 8 9
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%Element by Element Arithmetic VS Matrix Arithmetic
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A * B % Matrix multiplication
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A .* B % Multiple each element in A by its corresponding element in B
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%Plotting
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x = 0:.10:2*pi % Creates a vector that starts at 0 and ends at 2*pi with increments of .1
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y = sin(x)
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plot(x,y)
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xlabel('x axis')
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ylabel('y axis')
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title('Plot of y = sin(x)')
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axis([0 2*pi -1 1]) % x range from 0 to 2*pi, y range from -1 to 1
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plot(x,y1,’-’,x,y2,’--’,x,y3,’:’) % For multiple functions on one plot
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% .mat files
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% Save the variables in your Workspace
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%M-file Scripts
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%A script file is an external file that contains a sequence of statements.
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%Better than typing your code in the Command Window
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%Have .m extensions
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%M-file Functions
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%Programs that accept inputs and return an output
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%Have .m extensions
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% double_input.m - naming your ,m file the same as you call it in the file is required
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function output = double_input(x)
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%double_input(x) returns twice the value of x
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output = 2*x;
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end
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double_input(6) % ans = 12
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%User input
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a = input('Enter the value: ')
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%Reading in data
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fopen(filename)
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%Output
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disp(a) % Print out the value of variable a
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disp('Hello World') % Print out a string
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fprintf % More control display to Command Window
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%Conditional statements
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if a > 15
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disp('Greater than 15')
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elseif a == 23
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disp('a is 23')
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else
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disp('neither condition met')
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end
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%Looping
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for k = 1:5
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disp(k)
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end
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k = 0;
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while (k < 5)
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k = k + 1;
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end
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%Connecting to a MySQL Database
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dbname = 'database_name';
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username = 'root';
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password = 'root';
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driver = 'com.mysql.jdbc.Driver';
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dburl = ['jdbc:mysql://localhost:8889/' dbname];
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javaclasspath('mysql-connector-java-5.1.xx-bin.jar'); %xx depends on version, download available at http://dev.mysql.com/downloads/connector/j/
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conn = database(dbname, username, password, driver, dburl);
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sql = ['SELECT * from table_name where id = 22'] %Example sql statement
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a = fetch(conn, sql) %a will contain your data
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% Common math functions
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sin(x)
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cos(x)
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tan(x)
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asin(x)
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acos(x)
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atan(x)
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exp(x)
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sqrt(x)
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log(x)
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log10(x)
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abs(x)
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min(x)
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max(x)
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ceil(x)
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floor(x)
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round(x)
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rem(x)
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rand
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randi
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% Common constants
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pi
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NaN
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inf
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% Common matrix functions
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zeros(m,n) % m x n matrix of 0's
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ones(m,n) % m x n matrix of 1's
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diag(A) % Extracts the diagonal elements of a matrix
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eye(m,n) % Indentity matrix
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inv(A) % Inverse of matrix A
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det(A) % Determinant of A
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eig(A) %Eigenvalues and eigenvectors of A
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isempty(A) % Tests if array is empty
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isequal(A, B) %Tests equality of two arrays
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numel(A) %Number of elements in matrix
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```
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## More on Matlab
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* The official website [http://http://www.mathworks.com/products/matlab/](http://www.mathworks.com/products/matlab/)
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