# for loop assistance selecting the correct values

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Eddy Ramirez on 31 Mar 2021
Commented: Eddy Ramirez on 2 Apr 2021
Greetings,
I am runnig the for loop below and it seems that it works, but one issue that I am havng is that I think the for loop is taking the lenght (in this case taking 10) and solving for the matrix and equations. Is there a way for me to see it up where it reads each individual angle from 1 through 10. I tried to do "for i=1:10" and keeping everything else the same, but it does not work. I want the for loop to run angles 1 thorugh 10 through all the equations where I end up with 10 different results not just one(which is what I am getting since I am using "length") Thank you in advance for your assistance
theta=1:10;
m=cosd(theta);
n=sind(theta);
m2=m.^2;
n2=n.^2;
for i=1:length(theta)
T=[m2(i) n2(i) 2*m(i)*n(i);
n2(i) m2(i) -2*m(i)*n(i);
-m(i)*n(i) m(i)*n(i) m2(i)-n2(i)];
sigma1=sym('sigma_1');
sigma2=sym('sigma_2');
tau6=sym('tau_6');
stress=[sigma1; sigma2; tau6];
sigmax=0;
sigmay=0;
tau5=sym('taus');
stress_rotation=[sigmax; sigmay; tau5];
equation=stress==T*stress_rotation;
solution=solve(equation, stress);
sigma1_f=vpa(solution.sigma_1);
sigma2_f=vpa(solution.sigma_2);
tau6_f=vpa(solution.tau_6);
end

Walter Roberson on 31 Mar 2021
theta=1:10;
m=cosd(theta);
n=sind(theta);
m2=m.^2;
n2=n.^2;
for i=1:length(theta)
T=[m2(i) n2(i) 2*m(i)*n(i);
n2(i) m2(i) -2*m(i)*n(i);
-m(i)*n(i) m(i)*n(i) m2(i)-n2(i)];
sigma1=sym('sigma_1');
sigma2=sym('sigma_2');
tau6=sym('tau_6');
stress=[sigma1; sigma2; tau6];
sigmax=0;
sigmay=0;
tau5=sym('taus');
stress_rotation=[sigmax; sigmay; tau5];
equation=stress==T*stress_rotation;
solution=solve(equation, stress);
sigma1_f(i)=vpa(solution.sigma_1);
sigma2_f(i)=vpa(solution.sigma_2);
tau6_f(i)=vpa(solution.tau_6);
end
plot(theta, [sigma1_f(:), sigma2_f(:), tau6_f(:)]./tau5);
legend({'sigma1_f', 'sigma2_f', 'tau6_f'}); Eddy Ramirez on 2 Apr 2021
makes sense which is why theta 0 wont work either... truly appreciate all your help and time!