Basics
clc % clear command window
clear % clear memory
; % no result displayed if command is terminated with semikolon
3.1 Comments
% Single Comment
%{
multi
line
comment!
%}
% MATRICES / VECTORS
ones(3,4) generate 3x4 matrix filled with ones
zeros(3,4) generate 3x4 matrix filled with zeros
m = [1,2 ; 3,4]
[1 2]
[3 4]
m[1,2] get value of 1st row, 2nd column of matrix m
m[2,:] generates a vector with values of 2nd row
v = 1:5 generate vector v = [1 2 3 4 5]
numel(x) counts number of elements in x (works for vectors & matrix)
COMMENTS
% code on current line will be ignored
%% new comment-section
CONSTANTS
pi Pi
exp(1) e^1 (Eulersche Zahl)
FUNCTIONS (anonymous)
name =@(x) x^2; define function name=x^2 with x as input
name(2); computes functionvalue of function name at x=2
name2 =@(a,b) a^2 + b^2; define function f=a^2+b^2 with a and b as input
name2(2,3); computes functionvalue of function name2 at 2
IMPLIZIT PLOTS!
ezplot('x.^3 + x.*y + y.^2 - 36',[-10 10 -10 10]);
[x,fval] = fminsearch(@(x) x(1).^2 + x(2).^2, [2 1])
WRITE TO CONSOLE
fprintf('message with %s', 'asd');
disp('message with asd');
ERROR MESSAGE IN RED
fprintf(2,'my error(warning) message in RED!\n' );
CELLS
C = cell(3,1); % initialize cellarray (3x1)
C(1) = cellstr('test1'); % convert string to cellarray
C(3) = cellstr('test2'); % convert string to cellarray
disp(C); % display cellarray (1 empty value)
disp(C(~cellfun('isempty',C)) % delete empty entries
% convert cell to string
C = cell({'t1','t2',''}); % generate cell
str1 = char(C(1)); % convert 1st element of cell-array
str2 = char(C(2)); % convert 2nd element of cell-array
str3 = char(C(3)); % empty 1-by-0 matrix
2.2 Clearing Data
clc % Clear command window (does not clear variables)
clf % Clear figures
clear % Clear everything
clear all % Clear everything
clear <variable> % Clear single variable
2.3 Configure Output
format compact % Keeps output compact!
2.4 Stop Execution
Use CTRL-c to stop executing a particular command!
2.5 Precision
Precision is set to 15 digits by default. But you can configure that!
3. Basic MATLAB Syntax Reference
Click on New Script to start creating a new script!
3.1 Comments
% Single Comment
%{
multi
line
comment!
%}
You can also use CTRL-r to comment and CTRL-t to uncomment!
3.2 Variables
Everything is a double by default in MATLAB.
a = 5 % a is now 5! Yay!
Data Types:
- int8, int16, int32, int64
- char
- logical (Booleans)
- double
- single (Value without a decimal place)
- uint8
More On Variables
c1 = 'A'
class(c1) % Prints the class/type of the variable!
s1 = 'A string'
class(s1) % With single quotes, the class is 'char'
s2 = "A string"
class(s2) % With double quotes, the class is 'string'
5 > 2 % Logical 1
b1 = true % Logical 1
To get the maximum number you can store, you can use these! The maximum and minimums differ depending on the number type. The example list I'm writing below is non-exhaustive.
% For ints
intmax('int8')
intmin('int8')
% For doubles
realmax
% For singles
realmax('single')
3.3 Basic Operations
I really shouldn't need to explain this... You can use MATLAB like a calculator, and the results can go into variables!
a = 1 + 2 + 3 + 4 + 5
5 + 5 % Add
5 - 5 % Subtract
5 * 5 % Multiply
5 / 5 % Divide
5 ^ 4 % Exponent
mod(5, 4) % Mod (get remainder)
% NOTE! MATLAB doesn't have increment and decrement operators. So you can't do stuff like a++, b--, etc.
3.4 Casting
v2 = 8
v3 = int8(v2) % Like so!
Just write the appropriate class identifier and use it like a function!
3.5 Printing and Displaying
% Use this to display vectors and numbers!
disp(some_vector_variable)
% Use this to print strings!
fprintf("Hello world!")
% sprintf prints as a string
sprintf('5 + 4 = %d\n', 5 + 4)
% With the %d here, it transplants the next variable argument into the string!
3.6 User Input
Using the ; suppresses the input printout after the user has entered the input!
Note:
"might not work in some versions of MATLAB as a string delineator. Use'in that case.
String Input
% String Input
% Notice the '' escapes the second quote
name = input('What''s your name : ', 's');
% Let's use this if statement to print the input out! (~ means not)
if ~isempty(name)
fprinf('Hello %s\n', name)
end
Vector Input
vInput = input('Enter a vector : ');
disp(vInput)
3.7 Useful Math Functions
help elfun for a whole list of math functions
randi([10, 20]) % Random int
abs(-1) % Returns 1
floor(2.45) % Returns 2
ceil(2.45) % Returns 3
round(2.45) % Returns 2
exp(1) % e^x
log(100) % Log base e (ln)
log10(100) % Log base 10
log2(100) % Log base 2
sqrt(100) % Square root
deg2rad(90)
rad2deg(3.14)
3.8 Conditionals
> % More than
< % Less than
>= % More than or equal to
<= % Less than or equal to
== % Equal to
~= % Not equal to
|| % Or
&& % And
~ % Not
If block
if <condition>
<do something>
elseif <condition>
<do something else>
else
<do something entirely different>
end % REMEMBER TO END!!!
Switch Statement
switch score
case 1
disp("Aw")
case 2
disp("Better")
case 3
disp("You get the point")
otherwise
disp("WHO NAMED IT OTHERWISE OMG")
end % REMEMBER TO END
3.9 Vectors
They're one dimensional rows or columns!
THE INDEXING FOR MATLAB STARTS AT 1, NOT 0!!!!
% Row Vectors
vector_1 = [5 3 2 1] % Yep!
vector_2 [5, 3, 2, 1] % Both are valid ways!
% Column Vectors
vector_3 = [5; 3; 2; 1]
% Index into the vectors
vector_1(1) % 5
vector_1(end) % 1 (Last value)
vector([1 2 3]) % Get first, second, and third value in vector
% Get range
vector_1(1:3) % First to third
% Change at index
vector_1(1) = 6
% Transpose Vector
a = [1 2 3]
a' % This is now 1, 2, 3 as a column!
Vector Operations
a = [2; 3; 4]
b = [1 2 3]
a * b
% 2 4 6
% 3 6 9
% 4 8 2
3.10 Vector Methods
vector_1 = [1 2 3 4 5]
length(vector_1)
sort(vector_1, 'descend')
% Create ranges
5 : 10 % Gives you [5 6 7 8 9 10]
2 : 2 : 10 % Gives you [2 4 6 8 10]
% Concatenate
a = [1 2 3]
b = [4 5 6]
[a b] % [1 2 3 4 5 6]
% Dot Product (Either...)
a * b' % Transpose as needed
dot(a, b) % Self explanatory
% Cross Product
cross(a, b) % Nice
% Linspace
linspace(1, 20, 4) % Generates 4 numbers equally spaced between 1 and 20
% Logspace
logspace(1, 3, 3) % Like linspace, but the spacing is logarithmic
3.11 Matrices
It's MATLAB, not Vector lab.
matrix_a = [2 3 4; 4 6 8] % 2 rows, 3 columns (2x3)
length(matrix_a) % Gets you 3 (columns)
numel(matrix_a) % Number of values in matrix (6)
size(matrix_a) % Rows, then Columns (2 3)
% Generate random matrices!
randi([10, 20], 2)
% Index into matrices
a = [1 2 3; 4 5 6; 7 8 9]
a(1, 2) = 22 % Index into single value
a(1, :) = 25 % Change all row values
a(:, 2) % Change all column values
a(end, 1) % Last row
a(1, end) % Last column
% To delete a value, just literally put a semicolon at the end.
a(1, 2) = ;
% Multiply matrices
a * b
% Element-wise multiplication
a .* b % Take note of the period!
% Other matrix stuffffff
a - b
a + b
3.12 Matrix Methods
The list is not exhaustive!
Construction
Use the help command to find out how these work! They're overloaded functions.
eye()
ones()
zeros()
diag()
Mathematical Operations
sqrt(a) % Square root all values in matrix
sum(a) % Sum all columns
sum(a, 'all') % Sum all entries
prod(a) % Multiply all column values
cumsum(a, 'reverse') % Cumulative sum. First row stays the same, each row after is the sum of the preceding and current row (reverse makes it go in reverse)
cumsum(a) % Or if you don't want it reversed..
cumprod(a) % Cumulative product.
det() % Determinant
inv() % Inverse
Conditionals and Indexing
isequal(a, b) % Check for equality
a > 3 % Apply conditional to all entries
find(a > 24) % Gives you index of entries that fulfill the condition
Transformations
fliplr(a) % Flip left to right
flipud(a) % Flip up down
rot90(a) % Rotate 90 degrees
rot90(a, 2) % Rotate 180 degrees
reshape(a, 2, 6) % Reshape into 2x6, it's like numpy!
repmat(a, 2, 1) % Duplicate matrix into new matrix. Eg. If original matrix was 3x3, doing repmat(a, 2, 1) makes it 6x3
repelem(m3, 2, 1) % Duplicates ELEMENTS, so in this case, each element is duplicated twice in terms of the row
3.13 For Loops
For loops! It's pretty Pythonic. It iterates through a range.
% Loop from 1 to 10 and print it
for i = 1:10
disp(i)
end % REMEMBER TO END
% MORE EXAMPLES
% Print every value in matrix
a = [1 2 3; 4 5 6]
for i = 1:2
for j = 1:3
disp(a(i, j))
end
end
% Print for undetermined length
b = [6 7 8]
for i = 1:length(b)
disp(b(i))
end
3.14 While Loops
i = 1 % You must create the variable first!
while i < 20
if(mod(i, 2)) == 0
disp(i)
i = i + 1; % Semicolon suppresses the print
continue
end % This end is for i
i = i + 1;
if i >= 10
break
end
end
3.15 Cell Arrays
You can store data of multiple types
cell_A = {'Hi', 35, [25 8 19]}
cell_B = cell(5) % Create the cell spaces first
cell_A{1} % Get first element
cell_A{3}(2) % Index further
cell_A{4} = 'Something else'
cell_A(4) = ; % Delete
for i = 1:length(cell_A)
disp(cell_A{i})
end
% You can cast character arrays into cell arrays too!
a = ['A', 'BB', 'CCC']
char_array = cellstr(a)
3.16 Strings
Strings are vectors of characters!
str_1 = 'I am a string'
length(str_1)
% Index into a string
str_1(1)
str_1(3:4) % Slices
% Concatenation
str = strcat(str1, ' and now I''m longer!')
% Look for substring
strfind(str, 'a') % Returns indexes of all found substrings
% Replace string
strrep(str, 'longer', 'bigger')
% Split string
str_array = strsplit(str, ' ') % Splits at all spaces. Makes a string array
% Convert numbers to string
int2str(99)
num2str(3.14)
% Check for equality
strcmp(str1, str2)
% Check if is char
ischar('Rawr!11!!1')
% Check if a string is just made of letters
isletter('num 2') % Logical 0
isstrprop('word2', 'alpha')
% Check if string is made of alphanumeric characters
isstrprop('word2', 'alphanum') % Logical 1
% Sort
sort(str, 'descend')
% Delete whitespace (it's like .strip() in python)
strtrim(str)
% Lower and Uppercase conversion
lower(str)
upper(str)
3.17 Structures
Custom data types! Think C++ structs! Or Python dictionaries/maps.
methyl_struct = struct('name', 'methylDragon', ... % the ... lets you skip down to the next line (:
'species', ' Dragon')
disp(methyl_struct.name) % methylDragon
% Add a new field!
methyl_struct.sound = 'Rawr'
% Delete a field
methyl_struct = rmfield(methyl_struct, 'sound')
% Check if field exists
isfield(methyl_struct, 'species')
% Get all field names
fieldnames(methyl_struct)
% Store structures in vectors!
a(1) = methyl_struct
3.18 Tables
Tables are labelled rows of data in a table format
Get help table if you need help.
a = {'A'; 'B'; 'C'; 'D'};
b = [29; 42; 1; 2]
c = {'AA', 'BB', 'CC', 'DD'}
% Create a table!!! We'll specify a as the index now
test_table = table(a, b, c, 'RowName', a)
% You can do cool stuff with tables!
mean(test_table.b) % For example.. find the means
% Add new fields
test_table.d = [1; 2; 3]
% Pull specific entries
test_table({'A', 'B'}, :) % This defaults to using the RowName as indexer
% Pull specific entries, using another row
a(ismember(test_table.b, {29, 42},:)
3.19 File IO
% Let's just make a random matrix first
rand_matrix = randi([10, 50], 8)
% Let's save and load some files!
save sampdata.dat rand_matrix -ascii
load sampdata.dat
disp sampdata
type sampdata.dat
% We can save variables in a file as well!
save params % Leaving no arguments saves all variables you have on hand
load params
who % Display it on the screen
a = 123
save -append params a % This appends to the normal variable
3.20 Eval
If you know Python you should know what this does already.
Eval executes strings as code!
toExecute = spritnf('total = %d + %d', 5, 4)
eval(toExecute) % Executes it as:
% total = 5 + 4
3.21 Pausing
You can pause in MATLAB too! Think of it like Arduino delay() or Python time.sleep()
pause(5) % Pause for 5 seconds
pause off % Disable pause
pause on % Enable pause
4. Functional and OOP MATLAB
4.1 Functions
Functions have to come at the end of your file!
Local and global variable rules still apply! Local variables defined in functions don't change outside of the function! Just take note!
% Function to calculate volume
% The return is defined by the name preceding the =
% The name of the function is the name following the =
% In this case, the return is 'vol' and the function name is 'cylinderVol'
function vol = cylinderVol(radius, height)
vol = pi radius^2 * height
end
% Let's try another one! This time a function with no arguments
function randNum = getRandomNum
randNum = randi([1, 100])
end
% Return more than one value
[coneV, cylVol] = getVols(10, 20) % I'll call the function here, and define it below
function [coneVol, cylinVol] = getVols(radius, height)
cylinVol = pi * radius^2 * height
coneVol = 1/3 * cylinVol
end
% Variable Number of Arguments
function sum = getSum(varargin)
sum = 0;
for k = 1:length(varargin)
sum = sum + varargin{k}(1);
end
end
% Return variable number of outputs
function [varargout] = getNumbers(howMany)
for k = 1:howMany
varargout{1}(k) = k;
end
end
4.2 Anonymous Functions
No named functions! Think lambda in python
cubeVol = @ (l, w, h) l * w * h; % (input) output
a = cubeVol(2, 2, 2) % Gives you 8! Correct!
Pass Function to another Function
Think decorators!
Source: https://www.youtube.com/watch?v=NSSTkkKRabI
mult3 = @ (x) x * 3;
sol = doMath(mult3, 4)
function sol = doMath(func, num)
sol = func(num);
end
Returning Functions
Source: https://www.youtube.com/watch?v=NSSTkkKRabI
mult4 = doMath2(4);
sol2 = mult4(5)
function func = doMath2(num)
func = @(x) x * num;
end
4.3 Recursive Functions
They call themselves!
function val = factorial(num)
if num == 1
val = 1;
else
val = num * factorial(num - 1);
end
end
4.4 Classes
Static members are shared amongst all members of a class
classdef Shape
properties % Variables!!!
height
width
end
methods(Static)
function out = setGetNumShapes(data)
% Persistent values are shared by all objects also
persistent Var;
if isempty(Var)
Var = 0;
end
if nargin % Number of input arguments
Var = Var + data
end
out = Var;
end
end
methods
% Define a constructor
function obj = Shape(height, width)
obj.height = height
obj.width = width
obj.setGetNumShapes(1)
end
% Overloaded disp function
% If you don't know what overloading is, check my C++ tutorial. It basically overwrites the functionality of a pre-existing function if the argument number matches
function disp(obj)
fprintf('Height : %.2f / Width : %.2f\n', obj.height, obj.width)
end
function area = getArea(obj)
area = obj.height * obj.width;
end
% Overload Greater Than function
function tf = gt(obja, objb)
tf = obja.getArea > objb.getArea
end
end
end
Let's try using it!
a1 = Shape(10, 20)
disp(a1)
Shape.setGetNumShapes
a1.getArea
a2 = Shape(5, 10)
disp(a2)
Shape.setGetNumShapes
a1 > a2
4.5 Class Inheritance
classdef Trapezoid < Shape % Trapezoid inherits from Shape
properties
width2
end
methods
function obj = Trapezoid(height, width, width2)
obj@Shape(height,width) % The @ sign means you're taking it from the parent
% In this case we're using Shape's constructor!
obj.width2 = width2
end
function disp(obj)
fprint('Height : %.2f / Width : %.2f / Width2 : %.2f', obj.height, obj.width, obj.width2);
end
function area = getArea(obj)
area = (obj.height/2) * (obj.width + obj.width2);
end
end
end
Let's try it out!
a3 = Trapezoid(10, 4, 6)
disp(a3)
a3.getArea
5. Plotting
5.1 Plotting in MATLAB
Source: https://www.youtube.com/watch?v=NSSTkkKRabI
help plot for help!
xVals = 1:5
yVals = [2 4 8 5 9]
yVals2 = [1 5 7 6 8]
figure(1)
plot(xVals, yVals, 'g+', 'LineWidth', 2)
hold on % Draw over what was plotted, keep plot settings
plot(xVals, yVals2, 'k*')
legend('yVals', 'yVals2')
grid on % Turn grid on
xlabel('Days')
ylabel('Money')
title('Money Made Today')
figure(2)
bar(xVals, yVals, 'r')
% Colors : blue(b), black(k), cyan(c), green(g),
% magenta(m), red(r), yellow(y), white(y)
% Plot Symbols : . o x + * s d v ^ < > p h
% Line Types : -, :, -., - -
% Set font weights and the like
% gca is the axis object, gcf is the figure object
set(gca, 'FontWeight', 'bold', 'FontSize', 20, 'color', 'white');
set(gcf, 'color', 'white')
clf % Delete all figures
Example Sinusoid with Time
y = A.*cos(2*pi .* t/T - 2*pi .* x/lambda + phi0);
5.2 3D Plotting in MATLAB
3D Plots and Meshgrids
plot3() % Use this instead of plot2!
% Example
t = 0: pi/50 : 10*pi;
plot3(sin(t), cos(t), t)
% Meshgrids
meshgrid()
Surfaces
% Plot surfaces
cylinder()
sphere()
surf() % Plot a surface
isosurface() % For when plotting normal surfaces are too hard
contour() % Plot a contour map instead
Vector Fields
quiver() % 2D
quiver3() % 3D
colorbar % Add a colorbar!
6. Intermediate and Advanced Math
6.1 Vector Calculus
gradient()
divergence()
curl()
del2() % Discrete laplacian
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