MATLAB Function Generates the Vertices of a Regular N-gon with Line Segments

My task is to write a MATLAB function that generates the verticies of a regular n-gon and draws a line segment between each pair of verticies. The routine is only to plot one line segment at a time and the graph can only be generated by one "plot" command. I have a very rough outline of a program written up. There are some issues with the program. It plots one less vertice than n and I have no line segments connecting every vertice. Please help me to figure out where to go next with my program.

function e3(n)

%

%

t = linspace(0,1,n);

x = cos(t.*2*pi);

y = sin(t.*2*pi);

plot(x,y)

axis off

axis equal

Answer 1

[Ameer Hamza]

You need n+1 points, because points at angle of 0 and 2*pi are same.

t = linspace(0,1,n+1);

Can you explain, what do you mean by connecting all the vertices?

[Sophie Culhane]

For example, if x = [x1,x2,x3,x4] and y = [y1,y2,y3,y4], plot(x,y) should connect (x1,y1) and (x2,y2) with a line segment, connect (x2,y2) and (x3,y3) with a line segment, and connect (x3,y3) and (x4,y4) with a line segment.

[Ameer Hamza]

What is the reason for doing that? It will still look the same? Do you want to have lines with different colors?

[Sophie Culhane]

Sorry I should've specified more. The end product should look almost like a "star" shape with intercrossing line segments depending on the value of n.

[Ameer Hamza]

Can you draw an image with a simple polygon?

[Sophie Culhane]

[Ameer Hamza]

Try this

n = 15;

t = linspace(0,1,n+1);
x = cos(t.*2*pi);
y = sin(t.*2*pi);

[m1, m2] = ndgrid(1:n);
combs = unique(sort([m1(:) m2(:)],2), 'rows');
combs(diff(combs,[], 2)==0, :) = [];

hold on
for i = 1:size(combs,1)
    plot(x(combs(i,:)), y(combs(i,:)), 'b')
end

axis off
axis equal

[Sophie Culhane]

I am not able to use commands "hold on", "ndgrid", "sort", or "diff" as we have not learned those yet. Is there another way to go about this problem without those commands?

Answer 2

[Steven Lord]

You might find the degree-based trig functions sind and cosd useful. If you need to work exclusively with radians, the sinpi and cospi functions may be useful as well.

Finally for your iterative plotting either the comet or animatedline and addpoints functions may be of use.