I need a detailed explanation about this code

i started to learn matlab recently,and when i was studying about loops, one of my friend shared this code that can print a box with an X inside with the desired size

can someone provide explanation on this code?

[Cedric]

What part don't you understand specifically?

[Jan]

Please ask for specific details. It would be a waste of time to explain "clc", if you can read this by your own already:

help clc

Answer 1

[KL]

I suppose you read the documentation to understand what each command does and how a loop works. As far as this code is concerned, as you you can see, the idea is to plot a box with an 'x' inside it. It would have been easier to understand if the variables had much more meaningful names rather than 'x', 'n' and 'i'.

Anyway, here 'i' and 'x' are the row & column number of the box respectively and 'x' is decreasing from 'n' and 'i' is increasing from '1'. This is done so because you'd need to plot '*' along both diagonals to draw the letter 'x' inside the box.

So the while loop iterates through rows and the if condition in the beginning checks if it's the top or bottom most line of the square since in the case, '*' needed to plotted on every column, like a continuous line. then the for loop iterates over columns from 1 to n and plots a '*' if it's a diagonal position or a ' ' otherwise.

Got it?

[Triks King]

Thank you so much!

Answer 2

[Priyanka Akre]

% self organizing map Kohonen
% Programmed by Ammar AL-Jodah
clc
clear all
close all
for i=1:1000
    x1(i)=rand;
    x2(i)=rand;
end
for j1=1:10
    for j2=1:10
        w1(j1,j2)=rand*(0.52-0.48)+0.48;
        w2(j1,j2)=rand*(0.52-0.48)+0.48;
    end
end
figure(1)
plot(x1,x2,'.b')
hold on
plot(w1,w2,'or')
plot(w1,w2,'k','linewidth',2)
plot(w1',w2','k','linewidth',2)
hold off
title('t=0');
drawnow
no=1;
do=5;
T=300;
t=1;
while (t<=T)
    n=no*(1-t/T);
    d=round(do*(1-t/T));
    %loop for the 1000 inputs
    for i=1:1000
        e_norm=(x1(i)-w1).^2+(x2(i)-w2).^2;
        minj1=1;minj2=1;
        min_norm=e_norm(minj1,minj2);
        for j1=1:10
            for j2=1:10
                if e_norm(j1,j2)<min_norm
                    min_norm=e_norm(j1,j2);
                    minj1=j1;
                    minj2=j2;
                end
            end
        end
        j1star= minj1;
        j2star= minj2;
        %update the winning neuron
        w1(j1star,j2star)=w1(j1star,j2star)+n*(x1(i)- w1(j1star,j2star));
        w2(j1star,j2star)=w2(j1star,j2star)+n*(x2(i)- w2(j1star,j2star));
        %update the neighbour neurons
        for dd=1:1:d
            jj1=j1star-dd;
            jj2=j2star;
            if (jj1>=1)
                w1(jj1,jj2)=w1(jj1,jj2)+n*(x1(i)-w1(jj1,jj2));
                w2(jj1,jj2)=w2(jj1,jj2)+n*(x2(i)-w2(jj1,jj2));
            end
            jj1=j1star+dd;
            jj2=j2star;
            if (jj1<=10)
                w1(jj1,jj2)=w1(jj1,jj2)+n*(x1(i)-w1(jj1,jj2));
                w2(jj1,jj2)=w2(jj1,jj2)+n*(x2(i)-w2(jj1,jj2));
            end
            jj1=j1star;
            jj2=j2star-dd;
            if (jj2>=1)
                w1(jj1,jj2)=w1(jj1,jj2)+n*(x1(i)-w1(jj1,jj2));
                w2(jj1,jj2)=w2(jj1,jj2)+n*(x2(i)-w2(jj1,jj2));
            end
            jj1=j1star;
            jj2=j2star+dd;
            if (jj2<=10)
                w1(jj1,jj2)=w1(jj1,jj2)+n*(x1(i)-w1(jj1,jj2));
                w2(jj1,jj2)=w2(jj1,jj2)+n*(x2(i)-w2(jj1,jj2));
            end
        end
    end
    t=t+1;
    figure(1)
    plot(x1,x2,'.b')
    hold on
    plot(w1,w2,'or')
    plot(w1,w2,'k','linewidth',2)
    plot(w1',w2','k','linewidth',2)
    hold off
    title(['t=' num2str(t)]);
    drawnow    
end

[Priyanka Akre]

i want explaination of this code

[Image Analyst]

Contact Ammar AL-Jodah and ask him to explain it, and put in a lot more comments like any good professional programmer would have done. There is no excuse for bad code like that.