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diff --git a/matlab.html.markdown b/matlab.html.markdown index 9de41275..6dc9f697 100644 --- a/matlab.html.markdown +++ b/matlab.html.markdown @@ -1,27 +1,47 @@ --- language: Matlab +filename: learnmatlab.mat contributors: - ["mendozao", "http://github.com/mendozao"] - ["jamesscottbrown", "http://jamesscottbrown.com"] - + - ["Colton Kohnke", "http://github.com/voltnor"] + - ["Claudson Martins", "http://github.com/claudsonm"] --- -MATLAB stands for MATrix LABoratory. It is a powerful numerical computing language commonly used in engineering and mathematics. +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 +%% Code sections start with two percent signs. Section titles go on the same line. % Comments start with a percent sign. %{ -Multi line comments look +Multi line comments look something like this %} +% Two percent signs denote the start of a new code section +% Individual code sections can be run by moving the cursor to the section followed by +% either clicking the "Run Section" button +% or using Ctrl+Shift+Enter (Windows) or Cmd+Shift+Return (OS X) + +%% This is the start of a code section +% One way of using sections is to separate expensive but unchanging start-up code like loading data +load myFile.mat y + +%% This is another code section +% This section can be edited and run repeatedly on its own, and is helpful for exploratory programming and demos +A = A * 2; +plot(A); + +%% Code sections are also known as code cells or cell mode (not to be confused with cell arrays) + + % commands can span multiple lines, using '...': a = 1 + 2 + ... + 4 @@ -43,7 +63,7 @@ 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 of % turns off the code profiler +profile off % turns off the code profiler profile viewer % Open profiler help command % Displays documentation for command in Command Window @@ -62,18 +82,18 @@ 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; +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 +load('myFile.mat', 'y') % arguments within parentheses, separated 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 +% 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 @@ -103,7 +123,7 @@ a(2) % ans = y % Cells -a = {'one', 'two', 'three'} +a = {'one', 'two', 'three'} a(1) % ans = 'one' - returns a cell char(a(1)) % ans = one - returns a string @@ -113,7 +133,7 @@ A.c = [1 2]; A.d.e = false; % Vectors -x = [4 32 53 7 1] +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 @@ -121,9 +141,10 @@ 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 +x = [1:2:10] % Increment by 2, i.e. x = 1 3 5 7 9 % Matrices -A = [1 2 3; 4 5 6; 7 8 9] +A = [1 2 3; 4 5 6; 7 8 9] % Rows are separated by a semicolon; elements are separated with space or comma % A = @@ -132,7 +153,7 @@ A = [1 2 3; 4 5 6; 7 8 9] % 7 8 9 A(2,3) % ans = 6, A(row, column) -A(6) % ans = 8 +A(6) % ans = 8 % (implicitly concatenates columns into vector, then indexes into that) @@ -171,7 +192,7 @@ A(1,:) % All columns in row 1 % 4 5 42 % 7 8 9 -% this is the same as +% this is the same as vertcat(A,A); @@ -183,7 +204,7 @@ vertcat(A,A); % 4 5 42 4 5 42 % 7 8 9 7 8 9 -% this is the same as +% this is the same as horzcat(A,A); @@ -201,21 +222,23 @@ 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 +ctranspose(A) % Hermitian transpose the matrix % (the transpose, followed by taking complex conjugate of each element) +A' % Concise version of complex transpose +A.' % Concise version of transpose (without taking complex conjugate) -% Element by Element Arithmetic vs. Matrix Arithmetic +% 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 +% 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 +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 @@ -233,7 +256,7 @@ 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. +% 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 @@ -252,6 +275,8 @@ axis equal % Set aspect ratio so data units are the same in every direction scatter(x, y); % Scatter-plot hist(x); % Histogram +stem(x); % Plot values as stems, useful for displaying discrete data +bar(x); % Plot bar graph z = sin(x); plot3(x,y,z); % 3D line plot @@ -260,7 +285,7 @@ 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 +h = figure % Create new figure object, with handle h 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 @@ -271,9 +296,9 @@ 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 +% The function get 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') +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 @@ -298,8 +323,8 @@ 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 +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. @@ -312,11 +337,11 @@ load('myFileName.mat') % Load saved variables into Workspace % 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) +function output = double_input(x) %double_input(x) returns twice the value of x output = 2*x; end -double_input(6) % ans = 12 +double_input(6) % ans = 12 % You can also have subfunctions and nested functions. @@ -325,10 +350,10 @@ double_input(6) % ans = 12 % 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 +% 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: +% Example that returns the square of its input, assigned to the handle sqr: sqr = @(x) x.^2; sqr(10) % ans = 100 doc function_handle % find out more @@ -336,12 +361,12 @@ 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 +% 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) +fopen(filename) % Output disp(a) % Print out the value of variable a @@ -363,8 +388,8 @@ end for k = 1:5 disp(k) end - -k = 0; + +k = 0; while (k < 5) k = k + 1; end @@ -382,7 +407,7 @@ 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); +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 @@ -394,11 +419,11 @@ tan(x) asin(x) acos(x) atan(x) -exp(x) +exp(x) sqrt(x) log(x) log10(x) -abs(x) +abs(x) %If x is complex, returns magnitude min(x) max(x) ceil(x) @@ -409,6 +434,14 @@ rand % Uniformly distributed pseudorandom numbers randi % Uniformly distributed pseudorandom integers randn % Normally distributed pseudorandom numbers +%Complex math operations +abs(x) % Magnitude of complex variable x +phase(x) % Phase (or angle) of complex variable x +real(x) % Returns the real part of x (i.e returns a if x = a +jb) +imag(x) % Returns the imaginary part of x (i.e returns b if x = a+jb) +conj(x) % Returns the complex conjugate + + % Common constants pi NaN @@ -426,7 +459,7 @@ pinv(A) % calculate the pseudo-inverse 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 +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 @@ -452,22 +485,80 @@ flipud(A) % Flip matrix up to down [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 +max % largest component +min % smallest component length % length of a vector -sort % sort in ascending order -sum % sum of elements +sort % sort in ascending order +sum % sum of elements prod % product of elements -mode % modal value -median % median value -mean % mean value +mode % modal value +median % median value +mean % mean value std % standard deviation perms(x) % list all permutations of elements of x +find(x) % Finds all non-zero elements of x and returns their indexes, can use comparison operators, + % i.e. find( x == 3 ) returns indexes of elements that are equal to 3 + % i.e. find( x >= 3 ) returns indexes of elements greater than or equal to 3 + + +% Classes +% Matlab can support object-oriented programming. +% Classes must be put in a file of the class name with a .m extension. +% To begin, we create a simple class to store GPS waypoints. +% Begin WaypointClass.m +classdef WaypointClass % The class name. + properties % The properties of the class behave like Structures + latitude + longitude + end + methods + % This method that has the same name of the class is the constructor. + function obj = WaypointClass(lat, lon) + obj.latitude = lat; + obj.longitude = lon; + end + + % Other functions that use the Waypoint object + function r = multiplyLatBy(obj, n) + r = n*[obj.latitude]; + end + + % If we want to add two Waypoint objects together without calling + % a special function we can overload Matlab's arithmetic like so: + function r = plus(o1,o2) + r = WaypointClass([o1.latitude] +[o2.latitude], ... + [o1.longitude]+[o2.longitude]); + end + end +end +% End WaypointClass.m + +% We can create an object of the class using the constructor +a = WaypointClass(45.0, 45.0) + +% Class properties behave exactly like Matlab Structures. +a.latitude = 70.0 +a.longitude = 25.0 + +% Methods can be called in the same way as functions +ans = multiplyLatBy(a,3) + +% The method can also be called using dot notation. In this case, the object +% does not need to be passed to the method. +ans = a.multiplyLatBy(a,1/3) + +% Matlab functions can be overloaded to handle objects. +% In the method above, we have overloaded how Matlab handles +% the addition of two Waypoint objects. +b = WaypointClass(15.0, 32.0) +c = a + b ``` ## 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/) +* [The official website](http://www.mathworks.com/products/matlab/) +* [The official MATLAB Answers forum](http://www.mathworks.com/matlabcentral/answers/) +* [Loren on the Art of MATLAB](http://blogs.mathworks.com/loren/) +* [Cleve's Corner](http://blogs.mathworks.com/cleve/) |