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-rw-r--r--matlab.html.markdown162
1 files changed, 117 insertions, 45 deletions
diff --git a/matlab.html.markdown b/matlab.html.markdown
index 9de41275..25f762bb 100644
--- a/matlab.html.markdown
+++ b/matlab.html.markdown
@@ -1,22 +1,25 @@
---
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
@@ -43,7 +46,7 @@ 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
@@ -62,10 +65,10 @@ 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:
@@ -73,7 +76,7 @@ c = exp(a)*sin(pi/2) % c = 7.3891
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
+% 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 +106,7 @@ 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 +116,7 @@ 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 +124,10 @@ 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 +136,7 @@ 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 +175,7 @@ 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 +187,7 @@ 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 +205,23 @@ 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 +239,7 @@ 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 +258,8 @@ 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 +268,7 @@ 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 +279,9 @@ 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 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')
+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 +306,8 @@ 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 +320,11 @@ 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 +333,10 @@ 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 it's input, assigned to the handle sqr:
sqr = @(x) x.^2;
sqr(10) % ans = 100
doc function_handle % find out more
@@ -336,12 +344,12 @@ 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 +371,8 @@ end
for k = 1:5
disp(k)
end
-
-k = 0;
+
+k = 0;
while (k < 5)
k = k + 1;
end
@@ -382,7 +390,7 @@ 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 +402,11 @@ 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 +417,14 @@ 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 +442,7 @@ 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
@@ -452,17 +468,73 @@ 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
```