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diff --git a/matlab.html.markdown b/matlab.html.markdown new file mode 100644 index 00000000..507e9c85 --- /dev/null +++ b/matlab.html.markdown @@ -0,0 +1,260 @@ +--- +language: Matlab +contributors: + - ["mendozao", "http://github.com/mendozao"] +--- + +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 %} + +clear % Erases all your variables from memory +clc % Erases the writing on your Command Window +who % Displays all variables in memory +diary % History of session +ctrl-c % Abort current computation + +help command % Displays documentation for command in Command Window +lookfor command % Searches for a given command + + +% Output formatting +format short % 4 decimals in a floating number +format long % 15 decimals +fprintf + +% 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 +a = 2; b = 3; +c = exp(a)*sin(pi/2) % c = 7.3891 + +% 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 + +% 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 + + +% 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 seperated with a semi colon, each element is seperated with space or comma +% A = + +% 1 2 3 +% 4 5 6 +% 7 8 9 + +A(2,3) % ans = 6, A(row, column) +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(:, [3 1 2]) %Rearrange the columns of original matrix +%ans = + +% 3 1 2 +% 42 4 5 +% 9 7 8 + +A(1, :) =[] %Delete the first row of the matrix + +size(A) % ans = 3 3 + +A' % Transpose the matrix + +[A ; A] % Concatenation of matrices +%ans = + +% 1 2 3 +% 4 5 42 +% 7 8 9 +% 1 2 3 +% 4 5 42 +% 7 8 9 + + +%Element by Element Arithmetic VS Matrix Arithmetic +A * B % Matrix multiplication +A .* B % Multiple each element in A by its corresponding element in B + + +%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 + + +% .mat files +% Save the variables in your Workspace + +%M-file Scripts +%A script file is an external file that contains a sequence of statements. +%Better than typing your code in the Command Window +%Have .m extensions + + +%M-file Functions +%Programs that accept inputs and return an output +%Have .m extensions +% double_input.m - naming your ,m file the same as you call it in the file is required +function output = double_input(x) + %double_input(x) returns twice the value of x + output = 2*x; +end +double_input(6) % ans = 12 + +%User input +a = input('Enter the value: ') + +%Reading in data +fopen(filename) + +%Output +disp(a) % Print out the value of variable a +disp('Hello World') % Print out a string +fprintf % More control display to Command Window + +%Conditional statements +if a > 15 + disp('Greater than 15') +elseif a == 23 + disp('a is 23') +else + disp('neither condition met') +end + +%Looping +for k = 1:5 + disp(k) +end + +k = 0; +while (k < 5) + k = k + 1; +end + + +%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 +randi + +% Common constants +pi +NaN +inf + +% 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 +eye(m,n) % Indentity matrix +inv(A) % Inverse of matrix A +det(A) % Determinant of A +eig(A) %Eigenvalues and eigenvectors of A +isempty(A) % Tests if array is empty +isequal(A, B) %Tests equality of two arrays +numel(A) %Number of elements in matrix + + + +``` + +## More on Matlab + +* The official website [http://http://www.mathworks.com/products/matlab/](http://www.mathworks.com/products/matlab/) |