Least square fit.

a) Create an m-file that requests 5 arbitrary pairs of x and y values.
You should read one pair at a time and make a plot of these with (*) and perform a least square fit. The fit should be a linear function.
The pairs should lie in the interval 0-15.
If the user tries to write negative or larger values, please remind him/her of the limitations.

b) Make a node plot of the coordinates from the assignment 2a. The connection should be from point to point according to 1->2->3->4->5->1. Add yourself a
suitable scale on the x and y axis. Give it a title also .
The points should be marked with *. Hint: Use gplot.

my code:

i=1;

while i<=5

    A(i)=input('Enter any number:'); disp(A(i)) 

    if A(i)<0

        disp('Please enter a number between 0 and 15')  

   else if A(i)>15

        disp('Please enter a number between 0 and 15')

        else if A(i)>=0 && A(i)<=15

                i=i+1;

            else if A(i)<=15

                    i=i+1;

                end

            end

        end

    end

end

X=[A(1) A(2) A(3) A(4) A(5)];

disp(X);

i=1;

while i<=5

    B(i)=input('Enter any number:'); disp(B(i)) 

    if B(i)<0

        disp('Please enter a number between 0 and 15')

   else if B(i)>15

        disp('Please enter a number between 0 and 15')

        else if B(i)>=0

                i=i+1;

            else if B(i)<=15

                    i=i+1;

                end

            end

        end

    end

end

Y=[B(1) B(2) B(3) B(4) B(5)];

disp(Y);

for k=1:5,

xy(k,:)=[A(k) B(k)];

disp(xy(k,:));

end

k=[A(1)^2 A(1) 1 ; A(2)^2 A(2) 1 ; A(3)^2 A(3) 1 ; A(4)^2 A(4) 1 ; 
A(5)^2 A(5) 1];

disp(k);

x1=[A(1) ; A(2) ; A(3) ; A(4) ; A(5)];

disp(x1);

y=[B(1); B(2); B(3); B(4); B(5)];

disp(y);

a=inv(k'*k)*k'*y;

disp('a1:');

disp(a(1,1));

disp('a2:');

disp(a(2,1));

disp('a3:');

disp(a(3,1));

plot(x1,y,'r*'),grid on;

hold on

x=0:0.1:15;

t=0:0.1:15;

plot(t,a(1,1)*x.^2+a(2,1)*x+a(3,1),'-.')

title('quadratic function');

xlabel('x axis');

ylabel('y axis');

I want a graphical plot connecting these 5 pairs of data: from the first to second and from there to the third and so on.

how can I connect dots like that..

Thank you very much..

Answer 1

[bym]

change line 81 to read

plot(x1,y,'r*-'),grid on;

by the way, a is more efficiently calculated as

a = k\y;

[yahya aktas]

but I want a node plot of the coordinates.The connection from point to point according to 1->2->3->4->5->1.

[bym]

then just add the first point to x1 and y:

x1 = [x1;A(1)];

y = [y;B(1)];