How to stop for loop if E approximately = 0.8.?

Question

MOHD 2016-1-19

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/264332-how-to-stop-for-loop-if-e-approximately-0-8

编辑： Walter Roberson 2016-1-19

clc;
clear all;
close all;
[x,y]=meshgrid(-1:2/128:1);
circ=(x.^2+y.^2)<1;
A=ones(129,129);
B=A.*circ;
a1= 12849;
figure(1)
 imagesc(B),colormap gray;axis image;axis off;
   [x1,y1]=meshgrid(-1:2/128:1);
   for r=0:0.001:1
  circ1=(x1.^2+y1.^2)<r;
   C=B.*circ1;
   D=sum(sum(C));
   E=D/a1
  if (E ~= 0.8)
   end
   end
   figure(2)
   imagesc(C),colormap gray;axis image;axis off;

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Answer 1

John D'Errico 2016-1-19

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/264332-how-to-stop-for-loop-if-e-approximately-0-8#answer_206683

在 MATLAB Online 中打开

tol = 1.e-12;
[x1,y1]=meshgrid(-1:2/128:1);
for r=0:0.001:1
  circ1=(x1.^2+y1.^2)<r;
  C=B.*circ1;
  D=sum(sum(C));
  E=D/a1;
  if abs(E - 0.8) <= tol
    break
  end
end
figure(2)
imagesc( C ),colormap gray;axis image;axis off;