Why zero values in matrix

Question

Milan 2022-10-30

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1839443-why-zero-values-in-matrix

评论： Stephen23 2022-10-30

%hello, here eventhough matrix components are not zero, I am getting zero values when I put A a very large number. %Is there any way to avoid such?

E = 1;
I_z = 1;
%E_Iz = E*I_z;
R = 1;
L = R; %R
%A = 1;
A = 10^9; %so that axial strain is very small 
% K1 = A*E/L;
% K2 = 12*E*I_z/L^3;
% K3= 6*E*I_z/L^2;
% K4 = 4*E*I_z/L;
% K5 = 2*E*I_z/L; 
% for element 1
Ke_1_local = [A*E/L 0 0 -A*E/L 0 0;
    0 12*E*I_z/L^3 6*E*I_z/L^2 0 -12*E*I_z/L^3 6*E*I_z/L^2;
    0 6*E*I_z/L^2 4*E*I_z/L 0 -6*E*I_z/L^2 2*E*I_z/L;
    -A*E/L 0 0 A*E/L 0 0;
    0 -12*E*I_z/L^3 -6*E*I_z/L^2 0 12*E*I_z/L^3 -6*E*I_z/L^2;
    0 6*E*I_z/L^2 2*E*I_z/L 0 -6*E*I_z/L^2 4*E*I_z/L ]
Ke_1_local = 6×6
1.0e+09 *

    1.0000         0         0   -1.0000         0         0
         0    0.0000    0.0000         0   -0.0000    0.0000
         0    0.0000    0.0000         0   -0.0000    0.0000
   -1.0000         0         0    1.0000         0         0
         0   -0.0000   -0.0000         0    0.0000   -0.0000
         0    0.0000    0.0000         0   -0.0000    0.0000

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Answer 1

Walter Roberson 2022-10-30

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1839443-why-zero-values-in-matrix#answer_1087438

编辑：Walter Roberson 2022-10-30

在 MATLAB Online 中打开

you overlooked the 1.0e+09 * at the top of the display. Those 0.0000 are not true zeros, they are 1.0e+09 * a number that is 0.0000 to four decimal places.

I suggest that you give the command

format long g

and then ask to display the matrix

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Milan 2022-10-30

I see, I tried it and it worked, thanks for your help!

Stephen23 2022-10-30

"I mean for example value at 2, 2 is zero right..."

No, it is not. If the value is exactly zero then MATLAB displays it as "0". The trailing zero digits of "0.0000" tell us that value is not exactly zero, but that the trailing digits are zero when displayed with four digits after the decimal point.

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