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Plotting curves with increasing radius

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James
James el 21 de Ag. de 2013
Dear all,
I wanted to know if there is any way to plot a curve with increasing radius. This curve has to go around a circle.
Thanks for your help.
  8 comentarios
Image Analyst
Image Analyst el 21 de Ag. de 2013
Bring up your diagram somehow on the computer, be it in Photoshop or whatever. Type alt-Printscreen to capture the current window into the clipboard. Go to http://snag.gy and type control-V to paste it in. Note the URL it gives you and come back here and tell us what it is.
James
James el 21 de Ag. de 2013
@ Image Analyst: Thank you telling me how to do that. Below is the URL for the image. Hope it helps. The figure is of 3 different curves. The center is a circle, the other two I have the data for them but I am not sure not to plot them.

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Respuesta aceptada

Walter Roberson
Walter Roberson el 21 de Ag. de 2013
Your sample diagram look like spirals to me, other than that the radius might not be increasing linearly.
Use pol2cart() to switch between an (r, theta) form vs (x,y) coordinates.
  3 comentarios
Kelly Kearney
Kelly Kearney el 21 de Ag. de 2013
I see a circle and two spirals. Is this what you're looking for?
theta = linspace(pi/2+2*pi, pi/2, 100);
r = cell(3,1);
r{1} = ones(size(theta)); % The circle
r{2} = linspace(1, 0.5, 60); % Spiral in
r{3} = linspace(1, 1.5, 60); % Spiral out
for ii = 1:3
[x{ii}, y{ii}] = pol2cart(theta(1:length(r{ii})), r{ii});
end
xy = [x;y]; plot(xy{:}); axis equal;
James
James el 21 de Ag. de 2013
@Kelly Kearney: Thank you. That works perfect.

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Más respuestas (2)

Image Analyst
Image Analyst el 21 de Ag. de 2013
You say "I have the data for them" so why don't you just use the plot() function and plot them? Am I missing something???
  1 comentario
James
James el 21 de Ag. de 2013
Editada: James el 21 de Ag. de 2013
I have cropped the curve and that does make it better but I cannot get it to plot the full circle. I tried using a circle function for the circle but that failed too. Here is my code:
vehicle.a = 1.4; vehicle.b = 1.6; vehicle.m = 1600; vehicle.k = 1.5;
vehicle.l = vehicle.a + vehicle.b; vehicle.I = vehicle.m*vehicle.k^2;
vehicle.Cf = 6e4; vehicle.Cr = 6e4; vehicle.Ct = vehicle.Cf + vehicle.Cr;
% steering characteristics of the vehicle
steer.u = 1:1:40;
steer.a = [1.4 1.5 1.6]; steer.b = [1.6 1.5 1.4];
for i = 1:3
loop.a = steer.a(i);
loop.b = steer.b(i);
steer.s (:,i) = (loop.a*vehicle.Cf - loop.b*vehicle.Cr)/vehicle.Ct;
end
% Relations of turn radius and vehicle speed for constant steer angle
steer.delta = degtorad (3);
for j = 1:3
loop.s = steer.s(j);
for i = 1:40
loop.Vx = steer.u(i);
steer.R(i,j) = (vehicle.l/steer.delta)*(1-(((vehicle.Ct*loop.s*vehicle.m)/(2*vehicle.l^2*vehicle.Cf*vehicle.Cr))*loop.Vx^2));
end
end
% Change in turn radius with vehivle speed
loop.R = 50;
for j = 1:3
loop.s = steer.s(j);
for i = 1:40
loop.Vx = steer.u(i);
steer.delta(i,j) = (vehicle.l/loop.R)*(1-(((vehicle.Ct*loop.s*vehicle.m)/(2*vehicle.l^2*vehicle.Cf*vehicle.Cr))*loop.Vx^2));
end
end
for i = 1:3
steer.r = abs(steer.delta(:,i));
[loop.r,loop.theta] = spiral(steer.r);
steer.radius(:,i) = loop.r(:,1);
steer.theta(:,i) = loop.theta(:,1);
end
%Change of turning with increase of vehicle speed.
figure (4)
hold on
plot(steer.radius(:,1),steer.theta(:,1),'r')
plot(steer.radius(:,2),steer.theta(:,2),'b')
plot(steer.radius(:,3),steer.theta(:,3),'g')
title('Change of turning with increase of vehicle speed')
axis('equal')
hold off
The code is not yet cleaned up but that is no problem. Thank you for for taking such an interest in helping me.

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David Sanchez
David Sanchez el 21 de Ag. de 2013
Try this out:
[x,y] = meshgrid(1:150,1:100);
[th, rho] = cart2pol(x - 75,y - 50); % convert to polar
% spiral centered at (75,50)
Img = sin(r/3 + th);
imagesc(Img); colormap(hot);
axis equal; axis off;
  1 comentario
James
James el 21 de Ag. de 2013
Thank you for your help, but I am not looking to plot a spiral. I wanted to plot a curve with the radius increasing from a fixed distance.

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