Plotting help, function only giving one point

Hello friends,

I'm trying to recreate the image of a spiral staircase attached but I cant seem to get my code working. I just get a blank graph. I don't know how my loop is just giving me one point. Please help!

function z=my_staircase(a,b,h,n)

for t=0:2*pi*n
    r=((a*b)*exp(-.04*t))/sqrt((b*cos(t)^2)+ (a*sin(t))^2);
    x=r*cos(t);
    y=r*sin(t);
    z=(h*t)/(2*pi*n);
end
hold on
 plot3(x,y,z)
    xlabel('x(m)'); ylabel('y(m)');zlabel('z(m)');
    grid on

Answer 1

[Star Strider]

It’s giving you one point because that’s all you’re asking it to do.

A few tweaks, including subscripting ‘x’, ‘y’ and ‘z’ and all will be well:

function z = my_staircase(a,b,h,n)
tv = 0:2*pi*n;
for k1 = 1:length(tv)
    t = tv(k1);
    r=((a*b)*exp(-.04*t))/sqrt((b*cos(t)^2)+ (a*sin(t))^2);
    x(k1)=r*cos(t);
    y(k1)=r*sin(t);
    z(k1)=(h*t)/(2*pi*n);
end
hold on
 plot3(x,y,z)
    xlabel('x(m)'); ylabel('y(m)');zlabel('z(m)');
    grid on
    view([-30  30])
end

Changing the view parameters (I added that) help too.

[Japoe25]

I sort of got something weird when I ran the code :S

[Star Strider]

I would change the ‘tv’ assignment to:

tv = linspace(0, 2*pi*n, 50*n);

That will smooth the plot.