Index exceeds array bounds

Question

Hesam Jokar 2021-6-27

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/866375-index-exceeds-array-bounds

评论： Image Analyst 2021-6-30

i have written a code which gets data at time t and location i in two for loops, and calculates parameters. i haven't assigned a size to the arrays.

for t=1:24
    Tfodeg(1,1)=20;Tfo(1,1)=293.15;Tfodeg(2,1)=20;Tfo(2,1)=293.15;Tpmh(1,1)=293;
    for i=1:16
        rho_i(t,i)=999.9-((4.48e-3).*(Tfodeg(t,i-1).^2)); 
        mu_i(t,i)=0.001.*exp(-1.6-(1150./Tfo(t,i-1))+((690/Tfo(t,i-1))^2));

first I have assigned the preliminiary conditions. when i run this, i get the error:

Index in position 2 is invalid. Array indices must be positive integers or logical values.

which was rational. so, i changed the code

for t=2:25
    Tfodeg(1,1)=20;Tfo(1,1)=293.15;Tfodeg(2,1)=20;Tfo(2,1)=293.15;Tpmh(1,1)=293;
    for i=2:17
        rho_i(t,i)=999.9-((4.48e-3).*(Tfodeg(t,i).^2)); 
        mu_i(t,i)=0.001.*exp(-1.6-(1150./Tfo(t,i))+((690/Tfo(t,i))^2)); 

and i get this one:

Index in position 2 exceeds array bounds (must not exceed 1).

I think my code is mistake-free. anyone can help?

3 个评论
显示 1更早的评论隐藏 1更早的评论

Hesam Jokar 2021-6-28

thanks. I have defined the Tfodeg(t,i) before the for loops. You think i have to define it inside the loop?

G A 2021-6-30

It is difficult to say anythig without seing the whole code.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Image Analyst 2021-6-27

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/866375-index-exceeds-array-bounds#answer_734605

See the FAQ for a thorough discussion of the error:

https://matlab.fandom.com/wiki/FAQ#.22Subscript_indices_must_either_be_real_positive_integers_or_logicals..22

2 个评论
显示无隐藏无

Hesam Jokar 2021-6-28

Thanks

Image Analyst 2021-6-30

在 MATLAB Online 中打开

You say "I have defined the Tfodeg(t,i) before the for loops." but what are its dimensions. Before the for loop, do this

sizeTfo = size(Tfodeg)  % No semicolon
for t=2:25
    Tfodeg(1,1)=20;Tfo(1,1)=293.15;Tfodeg(2,1)=20;Tfo(2,1)=293.15;Tpmh(1,1)=293;
    for i=2:17
        rho_i(t,i)=999.9-((4.48e-3).*(Tfodeg(t,i).^2)); 
        mu_i(t,i)=0.001.*exp(-1.6-(1150./Tfo(t,i))+((690/Tfo(t,i))^2)); 

What does it say? My guess is that the second dimension is only 1m,, not 15. So to fix, either make it 15 or 16 or limit your inner for loop to the number of columns it has:

sizeTfo = size(Tfo)  % No semicolon
sizeTfodeg = size(Tfodeg)  % No semicolon
for t=2:25
    Tfodeg(1,1)=20;
    Tfo(1,1)=293.15;
    Tfodeg(2,1)=20;
    Tfo(2,1)=293.15;
    Tpmh(1,1)=293;
    lastIndex = min([sizeTfo(2), sizeTfodeg(2)])
    for i=2 : lastIndex
        rho_i(t,i)=999.9-((4.48e-3).*(Tfodeg(t,i).^2)); 
        mu_i(t,i)=0.001.*exp(-1.6-(1150./Tfo(t,i))+((690/Tfo(t,i))^2)); 