Receiving errors. Undefined variables etc

Question

Bria Johnson 2018-12-9

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https://ww2.mathworks.cn/matlabcentral/answers/434800-receiving-errors-undefined-variables-etc

重新打开： Star Strider 2018-12-10

Hello,

I am creating a code to find the mass of a beam after balancing it. I had 3 weights. Only 2 of 3 weights could be moved to balance the beam. I am having trouble with my code. I will attach my code and the errors below.

clear 
clc 
m1 = 1;
% mass 1, measured in kilograms.
m2 = 0.5;
% mass 2, measured in kilograms.
m3 = 0.2;
% mass 2, measured in kilograms.
rp = 0.87;
% distance of pivot, measured in meters.
r1 = 0.03;
% constant distance of mass 1, measured in meters.
r2 = [0.587 0.278 0.2 0.59 0.312 0.685 0.67 0.34 0.503 0.50 0.453]';
% distances obtained when moving mass 2.
r3 = [0.1289 0.2065 2.26 1.2 1.931 0.916 1.1 1.975 1.583 1.421 1.5 1.765]';
% distances obtained when moving mass 3.
l = 2.27;
% length of the beam measured in meters.
g = 9.8;
% gravitational constant measured in meters per seconds squared.
G = ones(length(m1), 2);
G(:,2) = m1;
m = G \ m2
rb = (0.5.*l-rp);
b = (m_b/m2).*rb-(m1/m2).*rb;
m_b =(m2/rp).*b *((-m1)/(rp));
sigma = sqrt(sum((m2-G*m).^2)./(length(m1)-2));
se1 = sigma.*sqrt(1./((length(m1)+mean(m1)^2/((length(m1)-1)*std(m1)^2))));
se2 = sigma.*sqrt(1./((length (m1)-1)*std(m1)^2));
Ci1=tinv(.975,length(m1)-2).*se1;
Ci2=tinv(.975,length(m1)-2).*se2;
% creating a line of best fit
X = [min(m1);1e-3;max(m1)]';
Y = m(1,1) + m(2,1).*X;
SE=sigma.*sqrt(1/length(m1)+(X-mean(m1)).^2./((length(m1)-1)*std(m1).^2));
Ci=tinv(.975,length(m1)-2).*SE;
figure(1)
clf
plot(m1, m2, 'ob')
hold on
% plotting the conidence intervals
plot (X, Y, 'R')
plot(X,Y+Ci,'g--')
plot(X,Y-Ci,'g--')
hold off
xlabel('$$-$$','interpreter','latex')
ylabel('$$-)$$','interpreter','latex')
print(figure(1), '-dpng', 'figure1')

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Star Strider 2018-12-9

You and your classmate seem to be having similar problems!

It would help significantly if you describe the problem you are having, preferably in some detail.

Bria Johnson 2018-12-9

The goal is to find the mass of the beam. I am having trouble with all of the variables/componets of the equation for mb. In my code I incorporated the equation for b, which is the y intercept however i am still receiving errors.

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