How to create helical sinusoidal plot in matlab

I want this plot

By using the below code I obtained the result as shown

dh = 0.5;

a = 42;

h = 20;

R = 45;

N = h/dh;

m = 1;

for n = 0:1:360*N

z(m)= 0-((dh/360)*n);

r = R -(((dh/360)*n)/tand(a));

x(m)=(r)*cosd(n);

y(m)=(r)*sind(n);

m = m+1;

end

plot3(x,y,z,'b')

axis equal

What changes should I do ?

Answer 1

[Chunru]

Is this what you want?

dh = 2; %0.5;   % adjust this to see more detains
a = 42;
h = 20;
R = 45;
N = h/dh;
m = 1;
for n = 0:1:360*N
    z(m)= 0-((dh/360)*n) + .4*cosd(60*n);  % add oscilation about z
    r = R -(((dh/360)*n)/tand(a));
    x(m)=(r)*cosd(n);
    y(m)=(r)*sind(n);
    m = m+1;
end
plot3(x,y,z,'b')
axis equal