Basins Of Attraction - Newtons Method

Question

Layan Daoud Agha 2021-2-25

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/756479-basins-of-attraction-newtons-method

回答： Shraddha Jain 2021-3-3

When I run my code it gives me an error that I do not know how to fix. The error says "Index in position 1 exceeds array bounds." How can I fix this?

This is the code I used, I also have a separate code for the function NewtonRaphson in case you were wondering:

clc ; clear all
warning('off') 
% The roots
r1 = [-0.672 ;-0.6074] ;
r2 = [0 ;0] ;
r3 = [0.672 ;0.6074] ;
x = linspace(-1,1,200) ;
y = linspace(-1,1,200) ;
Xr1 = [] ; Xr2 = [] ; Xr3 = [] ; Xr4 = [] ;
Tolerance = 0.1;
for i = 1:length(x)
     for j = 1:length(y)
          X0 = [x(i);y(j)] ;
          X = NewtonRaphson(X0) ;
          
          if norm(X-r1)<Tolerance %measuring L2 Norm
             Xr1 = [X0 Xr1]  ;
          elseif norm(X-r2)<Tolerance
             Xr2 = [X0 Xr2] ;
          elseif norm(X-r3)<Tolerance
             Xr3 = [X0 Xr3] ;
          else               
             Xr4 = [X0 Xr4] ;
          end
          
     end 
end
display(Xr1)
figure
set(gcf,'color','w') 
hold on
plot(Xr1(1,:),Xr1(2,:),'.','color','m') ;
plot(Xr2(1,:),Xr2(2,:),'.','color','b') ;
plot(Xr3(1,:),Xr3(2,:),'.','color','g') ;
plot(Xr4(1,:),Xr4(2,:),'.','color','k') ;
title('Basin of attraction for f(x,y) = 2x^3-y = 0 and 3y^3-x=0')
warning('on') 

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Answer 1

Shraddha Jain 2021-3-3

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/756479-basins-of-attraction-newtons-method#answer_637826

Hi Layan,

The error,

Index in position 1 exceeds array bounds

occurs when the index of the array accessed does not agree with the length of the array. Kindly check that the index at first position is neither less than 1 nor greater than the length of the array.