Quick Matlab

Posted on September 2, 2022

Tags: mathematica

1 Basics

1.1 Variables

Semicolon suppress output

a = 5;
b = 9;

% Saving variables to file
save datafile.mat %save all variable to file
save datafile.mat a  %save variable a to file

clear %clear variables

% Loading variable from file
load datafile.mat %load all variable from file
load datafile.mat a %load variable a from file

1.2 Take number input

mynum = input("put your number here:");
doublednum = mynum * 2

1.3 Take string/filepath input and show image

filepath = input("","s");
img = imread(filepath);
imshow(img);
imgR = imresize(img,0.5);
I = rgb2gray(imgR);
imshow(I)

1.4 Build your own function

Also necessary for code gen
Right-Click in folder >> New >> Script
Right-Click in folder >> New >> Function

In matlab you dont need to compile the function file. You can just run the main script that calls the function.

xaxis = 1:12
yaxis = rand(1,12)
plot(xaxis,yaxis)
hold on %plots both graph on top instead of separate plots
plot(xaxis,yaxis+0.1,"r--o") %r for red, -- with o as marker
hold off
plot(yaxis) %x-axis auto ranges from 1 to size of yaxis

imshow(filtr("DPlayer.png"))

2 Image label and training

Matlab use Simulink image labeler export will output: gTruth

trainingDataTable = objectDetectorTrainingData(gTruth)
acfDetector = trainACFObjectDetector(trainingDataTable,'NegativeSamplesFactor',2);
I = imread("C:\Users\User\Downloads\archive\shapes\squares\drawing(28).png");
bboxes = detect(acfDetector,I);
annotation = acfDetector.ModelName;
I = insertObjectAnnotation(I,'rectangle',bboxes,annotation);
figure
imshow(I)

2.1 Common math functions

%constants and functions
pi_ = pi
sin_ = sin(90)
eig_ = eig(ones(5))
abs_ = abs(-5)
imaginaryNum = 1i^2

2.2 Matrices and Vectors

%row vector
x1 = [3, 5, 7]
x2 = [3 5 7] %we can use comma or space

%col vector
y = [3;5;7] 
z = [1 2 3;4 5 6] %2 by 3 matrix

%select element in matrix
z(2,3) % element in position 2,3
z(:,3) % allrow,third column

2.2.1 Transpose

%Transpose using single  quote '
xT = [3 5 7]'

2.3 Matrix Operations

test1 = [3 5 7 12 10] %we can use comma or space

test1(1) %output 3, first element
test1(1) = 9 %change first element

test1(1:2) = [4 2] %change first 2 elements
test1([1 3]) %output 1st and 3rd element 

test1(end) %last element
test1(end-1) %next to last element 

test1 = [3 5 7 12 10] 
%logical indexing
test1 > 3 %outputs a mask
test1(test1 > 3)
test1(test1 == 3)
test1(test1 ~= 3)
test1(test1 > 3 & test1 < 7)
test1(test1 > 3 | test1 < 7)
test1(test1 ~= 3) = 99 %replace elem neq 3 with 99

2.4 Plotting

xaxis = 1:12
yaxis = rand(1,12)
plot(xaxis,yaxis)
hold on %plots both graph on top instead of separate plots
plot(xaxis,yaxis+0.1,"r--o") %r for red, -- with o as marker
hold off
plot(yaxis) %x-axis auto ranges from 1 to size of yaxis

3 Image label and training

Matlab use Simulink image labeler export will output: gTruth

trainingDataTable = objectDetectorTrainingData(gTruth)
acfDetector = trainACFObjectDetector(trainingDataTable,'NegativeSamplesFactor',2);
I = imread("C:\Users\User\Downloads\archive\shapes\squares\drawing(28).png");
bboxes = detect(acfDetector,I);
annotation = acfDetector.ModelName;
I = insertObjectAnnotation(I,'rectangle',bboxes,annotation);
figure
imshow(I)

4 Code generation

Right-Click in folder >> New >> Script
Right-Click in folder >> New >> Function

Code gen must be functions. But we can run any process inside the function file so we use the Script file to test the function.

function [myOutput] = filtr(myInput)
%FILTRFUNCTION Summary of this function goes here
%   Detailed explanation goes here
myOutput = eig(myInput)
end

filtr(rand(3,3))

Go to Apps >> Matlab Coder.

Selection function file path, filtrFunction.m NOT our script myscript.m
Defaults for entry point function
It will prompt To automatically define input types, call filtr or enter a script that calls filtr in the MATLAB prompt below: Here we select the script that CALLS our function which is myscript.m. Then click Autodefine Input Types.
Check for runtype issues by running the compiled function filtrFunction.mex on our caller script myscript.m
Build as C,C++, or mex