Index out of bounds

Question

bugatti79 2014-8-2

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/144454-index-out-of-bounds

评论： Star Strider 2014-8-4

采纳的回答： Star Strider

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Folks,

What is wrong with this simple code?

Fo=100;
wn=20;
k=2000;
m=5;
w=30;
x0=.1;
x0_dot=.1;
f_0=Fo/m;
for i=1:100;
       X(i)=Fo/(k-m*w(i)^2);
end  
 figure;
  plot(w,X);
  xlabel('w');
  ylabel('X');

I get the following error

Attempted to access w(2); index out of bounds because numel(w)=1.
Error in Example315pg326RAO (line 21)
       X(i)=Fo/(k-m*w(i)^2);

Thanks

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Answer 1

Star Strider 2014-8-2

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https://ww2.mathworks.cn/matlabcentral/answers/144454-index-out-of-bounds#answer_147184

Your w variable is defined as a constant scalar: w=30. You have to define w as a 100-element vector, because your code doesn’t make sense otherwise (specifically the loop that calculates X(i)).

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bugatti79 2014-8-4

Thanks

Star Strider 2014-8-4

My pleasure!

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Answer 2

Image Analyst 2014-8-2

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/144454-index-out-of-bounds#answer_147186

在 MATLAB Online 中打开

Is w a constant? Or does it change depending on what i is? If so, how? By the way, it doesn't even matter if you vectorize your code, though since you're plotting versus w it looks like it's supposed to be an array. I made it an array in the "fixed" code below:

fontSize = 24;
Fo = 100;
wn = 20;
k = 2000;
m = 5;
% Make w go from 30 to 60
w = linspace(30, 60, 100);
x0 = .1;
x0_dot = .1;
f_0= Fo / m;
X = Fo ./ (k-m*w.^2);
plot(w, X, 'b-', 'LineWidth', 3);
xlabel('w', 'fontSize', fontSize);
ylabel('X', 'fontSize', fontSize);
title('X vs. w', 'fontSize', fontSize);
grid on;
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);