problem with scatter/bubble plot

hi,

i have created a vector containing coordinates of a circle in a matrix.

i want to display these locations as dots in a plot.further i want to color these dots in a clockwise increasing color scheme. i have written a code but experienced a problem : the color vector which i created does not seem to be mapped linearly to my location points

code:

   matrix = ones(512,512); 
   mittelpunkt_x = 256; 
   mittelpunkt_y = 256; 
   radius = 33; 

for i=1:size(matrix,1) 
     for j = 1:size(matrix,2) 
         matrix(i,j) = norm([i j]-[mittelpunkt_x,mittelpunkt_y],2); 
          if matrix(i,j)<=radius 
          matrix(i,j)=0;%10; 
           elseif matrix(i,j)<radius+1 && matrix(i,j)>radius 
          matrix(i,j)=1; 
         else 
             matrix(i,j)=0; 
         end 

       end 
  end 

b=0.00490196078
[r,c]=find(matrix==1);

color=[b:b:1]; 

y=[r c]; 

scatter(r,c,50,color,'filled')

i hope someone can help me with this

g3rm9

Answer 1

[bym]

something like this?

t = 0:pi/6:2*pi
t(13)=[];
x = cos(t);
y = sin(t);
c = spring(12);
scatter(x,y,[],c,'filled')

[germ]

Wow thank you proecsm !

yes i searched for something like this. it seems a lot easier than my method of

getting the locations.

i still have some questions : what does the second line do(t(13)=[];)

and how would i get this animated(turn the circle). i thought of the circshift

command (c2=circshift(c, [-1, 0]);) but am not shure how to create a gif out of this: do i have to create 60 (using t = 0:pi/30:2*pi) single scatterplots and somehow merge them ?

or is there another way of doing this

[bym]

you will notice my original array contains both 0 and 2*pi. To avoid plotting that point twice, I just delete the last point.

t(13)=[] %delete the last point.

as far as animation, you'll have to do that in a loop. look at the documentation for

getframe()

[germ]

thank you alot !

my final code is :

t = 0:pi/30:2*pi

t(60)=[];

x = cos(t);

y = sin(t);

c = jet(60);

z = zeros(60,3);

z(1,:)=[1 0 0];

for j=1:60;

scatter(x,y,[],circshift(c, [-j,0]),'filled')

axis equal;

F(j) = getframe;

end

movie(F,2)

the only thing i wonder is why the 17th point seems to be missing

[bym]

second line should be:

t(61) = [ ];

Answer 2

[the cyclist]

I'm not sure I understand what the problem is. When I run your code, I see a circle with varying color going around it, which I assume is what you want. It may not look like a circle, because the displayed axes do not have equal aspect ratio. You may want to put the following code after your scatter() command:

 >> axis equal
 >> axis square

If that is not what you mean, then you will need to be more explicit by what "mapped linearly to my location points" means.

[germ]

thank you for the quick reply !

yes i may have not been very explicit with my question.

when i run the upper code i see the colored circle.what i want is a smooth flow from ie: yellow to red. through the whole circle. in the current plot the colorvariation from yellow to red only reaches from the 1 point to half of the circle then the color decreases in the second part ending with the 1 and last point being the same color.

at the current state i have modified my code to :

matrix = ones(50,50);

mittelpunkt_x = 25;

mittelpunkt_y = 25;

radius = 11;

for i=1:size(matrix,1)

for j = 1:size(matrix,2)

matrix(i,j) = norm([i j]-[mittelpunkt_x,mittelpunkt_y],2);

if matrix(i,j)<=radius

matrix(i,j)=0;%10;

elseif matrix(i,j)<radius+1 && matrix(i,j)>radius

matrix(i,j)=1;

else

matrix(i,j)=0;

end

end

end

%figure

%imshow(matrix,[0 10]);

[r,c]=find(matrix==1);

farbe=rand(1,60);

R = zeros(60,1);

G = zeros(60,1);

B = zeros(60,1);

R(:,1)=1;

G0=[1/60:1/60:1];

G=G0';

R(20,1)=0;

G(20,1)=0;

B(20,1)=0;

RGB = [R G B];

y=[r c]; %r=x-koordinate c=y-koordinate

z=matrix(:);

figure

scatter(r,c,50,RGB,'filled')

axis equal

axis square

R2 = R([60 1:59],1);

G2 = G([60 1:59],1);

B2 = B([60 1:59],1);

RGB2=[R2 G2 B2];

figure

scatter(r,c,50,RGB2,'filled')

axis equal

axis square

R3 = R2([60 1:59],1);

G3 = G2([60 1:59],1);

B3 = B2([60 1:59],1);

RGB3=[R3 G3 B3];

figure

scatter(r,c,50,RGB3,'filled')

R4 = R3([60 1:59],1);

G4 = G3([60 1:59],1);

B4 = B3([60 1:59],1);

RGB4=[R4 G4 B4];

figure

scatter(r,c,50,RGB4,'filled')

axis equal

axis square

for i want the circle to have 60 locations imitating a clock .

the second change i made is that i generated multiple plots cause i want to do a animation of the circle. means making it turn(i'm still not sure how to realize this but am working on it)

i hope you can imagine what i mean :)