Matrix display wrong value

Question

Young Lee 2023-6-7

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1979474-matrix-display-wrong-value

移动：Rik 2023-6-7

Screenshot 2023-06-07 164920.png

clear all
clc
% This is Tutorial Q1 Very important make sure the parameters are correct
L1=1000;
L2=2000;
b1=10;
h1=10;
b2=20;
h2=20;
A1=b1*h1;
A2=b2*h2;
E1=70e3;
E2=205e3;
c1=cos(deg2rad(0));
s1=sin(deg2rad(0));
c2=cos(deg2rad(-90));
s2=sin(deg2rad(-90));
I1=b1*h1^3/12;
I2=b2*h2^3/12;
k1 = [ A1*E1/L1 0 0 -A1*E1/L1 0 0; ...
    0 12*E1*I1/L1^3 6*E1*I1/L1^2 0 -12*E1*I1/L1^3 6*E1*I1/L1^2; ...
    0 6*E1*I1/L1^2 4*E1*I1/L1 0 -6*E1*I1/L1^2 2*E1*I1/L1; ...
    -A1*E1/L1 0 0 A1*E1/L1 0 0; ...
    0 -12*E1*I1/L1^3 -6*E1*I1/L1^2 0 (12*E1*I1)/L1^3 -6*E1*I1/L1^2; ...
    0 6*E1*I1/L1^2 2*E1*I1/L1 0 -6*E1*I1/L1^2 4*E1*I1/L1]
k1 = 6×6
1.0e+05 *

    0.0700         0         0   -0.0700         0         0
         0    0.0000    0.0035         0   -0.0000    0.0035
         0    0.0035    2.3333         0   -0.0035    1.1667
   -0.0700         0         0    0.0700         0         0
         0   -0.0000   -0.0035         0    0.0000   -0.0035
         0    0.0035    1.1667         0   -0.0035    2.3333
k2  = [ A2*E2/L2 0 0 -A2*E2/L2 0 0; ...
    0 12*E2*I2/L2^3 6*E2*I2/L2^2 0 -12*E2*I2/L2^3 6*E2*I2/L2^2; ...
    0 6*E2*I2/L2^2 4*E2*I2/L2 0 -6*E2*I2/L2^2 2*E2*I2/L2; ...
    -A2*E2/L2 0 0 A2*E2/L2 0 0; ...
    0 -12*E2*I2/L2^3 -6*E2*I2/L2^2 0 12*E2*I2/L2^3 -6*E2*I2/L2^2; ...
    0 6*E2*I2/L2^2 2*E2*I2/L2 0 -6*E2*I2/L2^2 4*E2*I2/L2]
k2 = 6×6
1.0e+06 *

    0.0410         0         0   -0.0410         0         0
         0    0.0000    0.0041         0   -0.0000    0.0041
         0    0.0041    5.4667         0   -0.0041    2.7333
   -0.0410         0         0    0.0410         0         0
         0   -0.0000   -0.0041         0    0.0000   -0.0041
         0    0.0041    2.7333         0   -0.0041    5.4667
lamd1 = [c1 s1 0 0 0 0; ...
    -s1 c1 0 0 0 0; ...
    0 0 1 0 0 0; ...
    0 0 0 c1 s1 0; ...
    0 0 0 -s1 c1 0; ...
    0 0 0 0 0 1];
lamd2 = [c2 s2 0 0 0 0; ...
    -s2 c2 0 0 0 0; ...
    0 0 1 0 0 0; ...
    0 0 0 c2 s2 0; ...
    0 0 0 -s2 c2 0; ...
    0 0 0 0 0 1];
K1 = lamd1'*k1*lamd1; % 1 1 1  2 2 2 
K2 = lamd2'*k2*lamd2;% 2 2 2  3 3 3 
Kg=zeros(9,9);
Kg(1:6,1:6) = K1;
Kg(4:9,4:9) = Kg(4:9,4:9)+K2;
Kgm = Kg;
% Loading condition[ r1x r1y r1th 2000 3000 -500 r3x r3y r3th]
%
F = [ 0 0 0 2000 3000 -500 0 0 0]'
F = 9×1
           0
           0
           0
        2000
        3000
        -500
           0
           0
           0
% boundary conditions F [u1 v1 th1 u2 v2 th2 u3 v3 th3 ]
% u1 v1 th1 u3 v3 th3 = 0 
%Modify Kg
Kg = Kg(4:6,4:6);
Fg = [2000 3000 -500]'
Fg = 3×1
        2000
        3000
        -500
U1 = Kg\Fg;   % u2 v2 th2
y1 = 5*10^-3;
x1 = 0;
B1 = [-1/L1 -y1*(12*x1-6*L1)/L1^3 -y1*(6*x1-4*L1)/L1^2 1/L1 y1*(12*x1-6*L1)/L1^3 ...
    -y1*(6*x1-2*L1)/L1^2 ]
B1 = 1×6
1.0e-03 *

   -1.0000    0.0000    0.0200    1.0000   -0.0000    0.0100
Exx1= B1*lamd1*[ 0 0 0 U1(1) U1(2) U1(3)]'
Exx1 = 2.8571e-04
sig1 = E1 *Exx1
sig1 = 19.9998

Need help on why matrix is displaying 0 on some arrays when it is not , for example on the attached screen shot, Kg(2,2) is 0,7 but matlab displays as 0

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Rik 2023-6-7

移动：Rik 2023-6-7

As you can see, there is a scaling factor at the start of the result. There you can see that you need to multiply each element by 1e5, meaning that 0.7 is rounded to 0e5 in the display.

If you want more control over how values are shown, you show read the documentation for the format function. It that is not enough, you will need to use fprintf.

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