How to plot different y values for different x values, provided the x and y values are to be generated in a loop?

Hello Everyone. I am unable to fetch the values of xy generated in the iteration process.

For every value of a, I want to plot ra. Following is my code, please help:

n=100;
b=6.9;
r=5;
y=(r-1)+0.5;
e=0;z=2;
U=9000;
for a=linspace(4500,U,500)
    q=2*pi*a*r;
    for m=0:n
        p=(4*q/pi)*((((-1)^m)/((2*m)+1))*(exp(-((2*m)+1)*(pi/(2*b))*z))*(cos(((2*m)+1)*(pi/(2*b))*y)));
        e=e+p;
        if (abs(p)/e)<(10^(-6))
            break
        end
        u=e;
        while z<=6
            z=z+1;
        end
    end
    ps=1000*((u/100)^2/2);
    ra=2*0.072/ps;
    plot(a,ra)
    hold on
end
hold off

Answer 1

[DGM]

This is a start:

n=100;
b=6.9;
r=5;
y=(r-1)+0.5;
e=0;z=2;
U=9000;

npoints = 500;
a = linspace(4500,U,500);
q = 2*pi*a*r;
ra = zeros(1,npoints);
for idx = 1:npoints
    for m=0:n
        p=(4*q(idx)/pi)*((((-1)^m)/((2*m)+1))*(exp(-((2*m)+1)*(pi/(2*b))*z))*(cos(((2*m)+1)*(pi/(2*b))*y)));
        e=e+p;
        if (abs(p)/e)<(10^(-6))
            break
        end
        u=e;
        while z<=6
            z=z+1;
        end
    end
    ps = 1000*((u/100)^2/2);
    ra(idx) = 2*0.072/ps;
end

plot(a,ra)

[ISHA ARORA]

Thank you, Sir. I have understood the mistake I was making. Still I have a doubt, that on plotting we are only getting one curve. But as we have also provided an equation for z, so why we aren't getting curves of ra v/s a for z varying from 3 to 6? Please explain.

[DGM]

The only thing you provided for z is

z = 2; 
% ...
while z<=6
    z=z+1;
end

Which does nothing but change the value of z from 2 to 7. Z is never any other value.

If z is supposed to be constant over each series, then:

n = 100;
b = 6.9;
r = 5;
y = (r-1)+0.5;
e = 0;
U = 9000;

npoints = 500;
a = linspace(4500,U,500);
q = 2*pi*a*r;
ra = zeros(4,npoints);
for z = 3:6
    for idx = 1:npoints
        for m = 0:n
            p = (4*q(idx)/pi)*((((-1)^m)/((2*m)+1))*(exp(-((2*m)+1)*(pi/(2*b))*z))*(cos(((2*m)+1)*(pi/(2*b))*y)));
            e = e+p;
            if (abs(p)/e)<(10^(-6))
                break
            end
            u = e;
        end
        ps = 1000*((u/100)^2/2);
        ra(z,idx) = 2*0.072/ps;
    end
    e = 0; % reset e
end
plot(a,ra)
legend({'aaa','bbb','ccc','ddd'})

There are four curves, and they are overlapping. If z is supposed to be doing something else, you'll have to decide what it's supposed to do.

[ISHA ARORA]

Sir, I have made changes in the code accordingly for the inclusion of 'z' as the factor affecting. But it is giving error:

Error using plot

Vectors must be the same length.

Error in online_sec (line 27)

plot(U,ra)

How do I eliminate this error, please help. Also, please explain, why in the previous code, e is reset to 0.

Follwing is my code:

n = 100;    %fixing the number of iterations
b = 6.9;    
r = 5;
y = (r-1)+0.5;
e = 0;
npoints = 500;
ra = zeros(5,npoints);
U=zeros(5,1);
for U=4500:500:9000     
    q=2*pi*(U/60)*r;    %linear vel conversion
    for z = 2:1:6
    for idx = 1:npoints
        for m = 0:n
           p=(4*q/pi)*((((-1)^m)/((2*m)+1))*(exp(-((2*m)+1)*(pi/(2*b))*z))*(cos(((2*m)+1)*(pi/(2*b))*y)));
            e = e+p;
            if (abs(p)/e)<(10^(-6)) %convergence check
                break
            end
            u = e;
        end
        ps = 1000*((u/100)^2/2);
        ra(z,idx) = (2*0.072/ps)*(10^(6));
    end
    e = 0; % reset e
    end
end
plot(U,ra)
legend({'z=2cm','z=3cm','z=4cm','z=5cm','z=6cm'})

[DGM]

n = 100;    %fixing the number of iterations
b = 6.9;
r = 5;
y = (r-1)+0.5;
e = 0;

U = 4500:500:9000;

npoints = numel(U);
ra = zeros(5,npoints);
for uidx = 1:npoints
    q = 2*pi*(U(uidx)/60)*r;    %linear vel conversion
    for z = 2:1:6
        for cidx = 1:npoints
            for m = 0:n
                p = (4*q/pi)*((((-1)^m)/((2*m)+1))*(exp(-((2*m)+1)*(pi/(2*b))*z))*(cos(((2*m)+1)*(pi/(2*b))*y)));
                e = e+p;
                if (abs(p)/e)<(10^(-6)) %convergence check
                    break
                end
                u = e;
            end
            ps = 1000*((u/100)^2/2);
            ra(z,cidx) = (2*0.072/ps)*(10^(6));
        end
        e = 0; % reset e
    end
end
plot(U,ra)
legend({'z=2cm','z=3cm','z=4cm','z=5cm','z=6cm'})

[ISHA ARORA]

Thank you so much, Sir.

Answer 2

[KSSV]

As you are plotting a point, you need to use marker.

n=100;
b=6.9;
r=5;
y=(r-1)+0.5;
e=0;z=2;
U=9000;
figure
hold on
for a=linspace(4500,U,500)
    q=2*pi*a*r;
    for m=0:n
        p=(4*q/pi)*((((-1)^m)/((2*m)+1))*(exp(-((2*m)+1)*(pi/(2*b))*z))*(cos(((2*m)+1)*(pi/(2*b))*y)));
        e=e+p;
        if (abs(p)/e)<(10^(-6))
            break
        end
        u=e;
        while z<=6
            z=z+1;
        end
    end
    ps=1000*((u/100)^2/2);
    ra=2*0.072/ps;
    plot(a,ra,'.b')
end
hold off

But it is suggested to store thevalues into an array and plot after the loop as @DGM suggested.

[ISHA ARORA]

Thank you, Sir. I have understood the mistake I was making. Still I have a doubt, that on plotting we are only getting one curve. But as we have also provided an equation for z, so why we aren't getting curves of ra v/s a for z varying from 3 to 6? Please explain.

[KSSV]

Becuase you are not plotting z. Include that plot also, so that you can get. But I feel z values lies far above the value of ra and plot doesn't look good.

[ISHA ARORA]

Thank you so much, Sir.