Solve "Index exceeds the number of array elements (1)", "Vectors must be the same length." errors

1 次查看（过去 30 天）

sookyung Kang 2020-7-15

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/565223-solve-index-exceeds-the-number-of-array-elements-1-vectors-must-be-the-same-length-errors

评论： Walter Roberson 2020-7-20

I'd like to solve those problems from under coding using A, B, and C relationships. If equation error can't be fixed, "B(i+1)=B(i)+((h.*q)/(k*T*E))*C(i)" can be used.

a = 0;
b = 1;
n = 110;
k = 8.61733*10^(-5); 
T = 300 ;
q = 1.60218*10^(-19);
E = 8.8542*10^(-12)
x= linspace(a,b,n);
h= x(2)-x(1);
A = zeros(size(x));
B = zeros(size(x));
for i = 0:n-1
    A(0)=3; 
    B(0)=1; 
    C(i)=2*x(i)+3;
    A(i+1)=A(i)-h.*B(i)-(0.5.*h.^2*q.*C(i))./(k*T*E);
    B(i+1)=B(i)+((h.*q)/(k*T*E))*0.5*(C(i)+C(i+1));%equation error
end
plot(transpose(x),A,'.')

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Tanmay Das 2020-7-15

Hi. Can you please try starting the index from 1 instead of 0 and go upto n in the for loop?

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Walter Roberson 2020-7-15

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/565223-solve-index-exceeds-the-number-of-array-elements-1-vectors-must-be-the-same-length-errors#answer_465986

在 MATLAB Online 中打开

a = 0;
b = 1;
n = 110;
k = 8.61733*10^(-5); 
T = 300 ;
q = 1.60218*10^(-19);
E = 8.8542*10^(-12)
x= linspace(a,b,n);
h= x(2)-x(1);
A = zeros(size(x));
B = zeros(size(x));
A(0+1)=3; 
B(0+1)=1; 
for i = 0:n-1
    C(i+1)=2*x(i+1)+3;
    A(i+1+1)=A(i+1)-h.*B(i+1)-(0.5.*h.^2*q.*C(i+1))./(k*T*E);
    B(i+1+1)=B(i+1)+((h.*q)/(k*T*E))*0.5*(C(i+1)+C(i+1+1));
end
plot(transpose(x),A,'.')

12 个评论
显示 10更早的评论隐藏 10更早的评论

sookyung Kang 2020-7-20

Yes. And no. I need to figure out that C equation by comparing theoretical equation as I didn't put this code.

Walter Roberson 2020-7-20

Which theoretical equation are you comparing to, and which result from your program are you comparing it to?

How do you know when you have reached and adequate solution?

请先登录，再进行评论。

更多回答（1 个）

Tanmay Das 2020-7-15

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/565223-solve-index-exceeds-the-number-of-array-elements-1-vectors-must-be-the-same-length-errors#answer_466175

在 MATLAB Online 中打开

Hi,

I have the understanding that you are facing trouble in indexing of arrays. Unlike C++ or Python, indexing starts from 1 in MATLAB. So if you write A(0), then it will throw error. The following code may be useful for your understanding:

a = 0;
b = 1;
n = 110;
k = 8.61733*10^(-5); 
T = 300 ;
q = 1.60218*10^(-19);
E = 8.8542*10^(-12)
x= linspace(a,b,n);
h= x(2)-x(1);
A = zeros(size(x));
B = zeros(size(x));
A(1)=3; 
B(1)=1; 
C = 2*x + 3
for i = 1:n-1    
    A(i+1)=A(i)-h.*B(i)-(0.5.*h.^2*q.*C(i))./(k*T*E);
    B(i+1)=B(i)+((h.*q)/(k*T*E))*0.5*(C(i)+C(i+1));%equation error
end
plot(transpose(x),A,'.')