Matlab - Plotting Circles

Hey guys (Hi)

I have the following problem:

Quote:

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Write a function m-file, PlotCircles.m, that can accept as input a vector, r,
having positive entries, and plots circles of radius r(i) on the same axis. If no input value for r is specified, the default is to plot a single circle with radius r = 1. Test your function by using r = 1:5.

Hints: Matlab commands that might be useful for this problem include max, min and any.

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My solution so far:

Quote:

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Code:

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function PlotCircles(r)

theta = linspace(0,2*pi,1000);

if nargin == 0
    r = 1;
end

for i = min(r):max(r)
  x = i*cos(theta);
  y = i*sin(theta);
  plot(x,y)
  axis square
  axis([-(r+1) (r+1) -(r+1) (r+1)])
end

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However when I input a vector as follows:

Quote:

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Code:

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EDU>> r = 1:5

r =

    1    2    3    4    5

EDU>> PlotCircles(r)
??? Error using ==> axis>LocSetLimits at 236
Vector must have 4, 6, or 8 elements.

Error in ==> axis at 96
                LocSetLimits(ax(j),cur_arg);

Error in ==> PlotCircles at 14
  axis([-(r+1) (r+1) -(r+1) (r+1)])

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And then it seems to draw only the first circle. Any help is appreciated. :)

Quote:

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Originally Posted by janvdl

Hey guys (Hi)

I have the following problem:



My solution so far:



However when I input a vector as follows:


And then it seems to draw only the first circle. Any help is appreciated. :)

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The simple answer is hold('on')/hold('off'), the following seems to work:

Code:

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function rv=PlotCircles(r)
  rv=[]
  theta = linspace(0,2*pi,100);
 
  if nargin == 0
    r = 1;
  end
 

  for i = 1:length(r)
    x = r(i)*cos(theta);
    y = r(i)*sin(theta);
    plot(x,y)
    axis square
    r0=max(r);
    axis([-(r0+1) (r0+1) -(r0+1) (r0+1)])
    hold('on');
  end
  hold('off');

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CB