I have problem to make code of deflection of beam

Question

minji park 2015-5-20

0
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https://ww2.mathworks.cn/matlabcentral/answers/217715-i-have-problem-to-make-code-of-deflection-of-beam

回答： Joseph Cheng 2015-5-20

I got this error, 'The variable 'y' appears to change size on every loop iteration. Consider preallocating for speed. please help me ...

function beam()

E = 210* 10^9;

L = 1;

W0= 4000;

I = (0.05 * 0.12^3) / 12;

    x=linspace(0,1,101);
    for i=1:101
        if  x(i) < 0.5
            y(i) = ((W0* L)/(4 * E * I)) * x(i)^2 - (W0/( 6 * E* I))* x(i)^3;
        else
            y(i) = ((W0*L)/(4 * E * I)) * x(i)^2 - (W0 / (6 * E * I)) * x(i)^3 + (W0 / (6 *E * I))*(x(i)- L/2)^3;
        end
    end
    plot(x,y);
    grid off;

end

Thanks

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Answer 1

Joseph Cheng 2015-5-20

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That is not an error. It is a warning. which based on the size of your function and number of iterations should not be an issue. It is saying if y will grow significantly large it may take some time to add additional data to it unless you pre-allocate the array.