the loop question for the for loop. k=1:n

I have a questions for a for loop questions.

this is a matlab code without for loop .

n=0.1;
b1=1;
b2=6;
b3=5;
b4=2;
b5=5;
b6=8;
y1=[1,0,2];
y2=[1,1,2];
y3=[1,2,1];
y4=[-1,3,-1];
y5=[-1,2,1];
y6=[-1,3,2];
a1=[1;0;0];
anew1=a1'+n*(b1-y1*a1)*y1;
anew2=anew1+n*(b2-y2*anew1')*y2;
anew3=anew2+n*(b3-y3*anew2')*y3;
anew4=anew3+n*(b4-y4*anew3')*y4;
anew5=anew4+n*(b5-y5*anew4')*y5;
anew6=anew5+n*(b6-y6*anew5')*y6
anew7=anew6+n*(b1-y1*anew6')*y1;
anew8=anew7+n*(b2-y2*anew7')*y2;
anew9=anew8+n*(b3-y3*anew8')*y3;
anew10=anew9+n*(b4-y4*anew9')*y4;
anew11=anew10+n*(b5-y5*anew10')*y5
anew12=anew11+n*(b6-y6*anew11')*y6
anew13=anew12+n*(b1-y1*anew12')*y1

and i want to use the for loop to make the code shorter and clear,

n=0.1;
b=[1;6;5;2;5;8;1;6;5;2;5;8;1];
y1=[1,0,2];
y2=[1,1,2];
y3=[1,2,1];
y4=[-1,3,-1];
y5=[-1,2,1];
y6=[-1,3,2];
y7=[1,0,2];
y8=[1,1,2];
y9=[1,2,1];
y10=[-1,3,-1];
y11=[-1,2,1];
y12=[-1,3,2];
y13=[1,0,2];
y=[y1;y2;y3;y4;y5;y6;y7;y8;y9;y10;y11;y12;y13];
a1=[1;0;0];
anew=[1,0,0];
for k=1:13 
    anew=anew+n*(b(k)-y(k,:)*(anew)')*y(k)
end

but i don't know why the two loop answes is different ,it should be same?

Answer 1

[Jos (10584)]

Your code is very unclear. Learn to use arrays and matrices. Rather than

b1 = 2 ; b2 = 4 ; b3 = ...
y1 = [1 2 3] ; y2 = [5 6 7] ; ...

use

b = [2 4 ...] % store b_k as position b(k)
y = [1 2 3 ; 5 6 7 ; ...] % store y_k in row y(k,:)

[QIWEI PAN]

Thank you ,

anew1=a1'+n*(b1-y1*a1)*y1;
anew2=anew1+n*(b2-y2*anew1')*y2;
anew3=anew2+n*(b3-y3*anew2')*y3;
anew4=anew3+n*(b4-y4*anew3')*y4;
anew5=anew4+n*(b5-y5*anew4')*y5;
anew6=anew5+n*(b6-y6*anew5')*y6
anew7=anew6+n*(b1-y1*anew6')*y1;
anew8=anew7+n*(b2-y2*anew7')*y2;
anew9=anew8+n*(b3-y3*anew8')*y3;
anew10=anew9+n*(b4-y4*anew9')*y4;
anew11=anew10+n*(b5-y5*anew10')*y5
anew12=anew11+n*(b6-y6*anew11')*y6
anew13=anew12+n*(b1-y1*anew12')*y1

I have to change this type of loop to

for k=1:13
    anew=anew+n*(b(k)-y(k,:)*(anew)')*y(k)
end

why the answers is different ?

[Stephen23]

"why the answers is different ?"

Because your code is too complex for such a simple task, makes it hard to understand, and hides bugs easily. You should follow Jos' advice and learn to use matrices and arrays instead.

Tip: whenever you write numbered variable names then you are doing something wrong and you should be using an array:

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

[Torsten]

anew=anew+n*(b(k)-y(k,:)*(anew)')*y(k,:)