MATLAB: How to use a Struct defined in previous calculation

loopstruct

Hello thanks for your time,
I am solving equations for the forces on this arm construction.
I calculate all the forces which occur on the upper arm by letting the angle (alpha) of the upper arm go from 0 to 90. This gives me for every set of equations a struct which contains some forces for every angle. For example like this:
F=100 %[N] 
hoekF=50
alpha=[1:1:90]
r=20
x=20.574
[hoeksup]=zeros(1,90)
for i=1:90
hoeksup(i)=asind((3*sind(135-alpha(i)))/(sqrt((x^2)+(3^2)-(2*x*3*cosd(135-alpha(i))))))
end 
Z=6
Y=(3*cosd(45))/2
syms F1x F1y F2
eqn1=(F*cosd(hoekF))==F1x+(F2.*cosd(alpha))
eqn2=(F*sind(hoekF))==F1y+(F2.*sind(alpha))
eqn3=(F2*cosd(alpha))*(3*sind(45))+(F2.*sind(alpha))*(3*cosd(45))+(F*sind(hoekF))*(Z)+(F*cosd(hoekF))*(Y)==0
for K = 1 : length(eqn1)
  q(K) = (vpasolve([eqn1(K),eqn2(K),eqn3(K)], [F1x,F1y,F2]))
end
I then use for example [q.F1x] in the following calculations.
My problem is the following:
The lowest arm can also vary from 0 to 90 (theta) independently of the upper arm. So I have to calculate the forces for every angle of the bottom arm with the all the possible forces from the upper arm. I was able to calculate all the forces at the top of the bottom arm and put them on a plot. I did the following: 
L1=6.243;
L2=2.0;
l1=2.1215;
theta=[1:1:90]
for i=1:90
syms F5 F6x F6y
eqn9=([c.F4x])+([d.F3x])==(F5.*cosd(theta(i)))+F6x+([d.Fp].*cosd(beta))
eqn10=([c.F4y])+([d.F3y])+(F5.*sind(theta(i)))+F6y==([d.Fp].*cosd(beta))
eqn11=(F5.*cosd(theta(i))*l1)+(F5.*sind(theta(i))*l1)+([d.F3y]*l1)+([d.Fp].*cosd(beta)*L1)==([d.F3x]*(L1-l1))+([c.F4x]*L1)
% eqn12=(F5.*cosd(theta)*(L1-l1))+(F6x*L1)==(F5.*sind(theta)*l1)+([d.F3x]*l1)+([d.F3y]*l1)
for K = 1 : length(eqn9)
  e(K) = (vpasolve([eqn9(K),eqn10(K),eqn11(K)], [F5,F6x,F6y]))
end
plot(theta,[e.F5],'r')
hold on 
end
This works for calculating all these forces (F5 F6x F6y) for every option of both angles, but I am unable to reuse all the calculated foces for calculations in lower parts of the bottom arm.
Is there a way to keep all the calculated structs e and use them later on?
gamma=theta-hoeksup
syms F7x F7y 
eqn12=([e.F5].*cosd(theta))+(Fp2.*cosd(gamma))==F7x
eqn13=([e.F5].*sind(theta))+(Fp2.*sind(gamma))==F7y

Best Answer

The easiest way is to store the structs arrays in a cell array and then later reuse them. For example
L1=6.243;
L2=2.0;
l1=2.1215;
theta=[1:1:90]
e_array = {}; % <--- initialize empty cell array
for i=1:90
    syms F5 F6x F6y
    eqn9=([c.F4x])+([d.F3x])==(F5.*cosd(theta(i)))+F6x+([d.Fp].*cosd(beta))
    eqn10=([c.F4y])+([d.F3y])+(F5.*sind(theta(i)))+F6y==([d.Fp].*cosd(beta))
    eqn11=(F5.*cosd(theta(i))*l1)+(F5.*sind(theta(i))*l1)+([d.F3y]*l1)+([d.Fp].*cosd(beta)*L1)==([d.F3x]*(L1-l1))+([c.F4x]*L1)
    % eqn12=(F5.*cosd(theta)*(L1-l1))+(F6x*L1)==(F5.*sind(theta)*l1)+([d.F3x]*l1)+([d.F3y]*l1)
    for K = 1 : length(eqn9)
      e(K) = (vpasolve([eqn9(K),eqn10(K),eqn11(K)], [F5,F6x,F6y]))
    end
    e_array{i} = e; % <--- store them for later use
    plot(theta,[e.F5],'r')
    hold on 
end
Then use them as follow
gamma=theta-hoeksup
syms F7x F7y
for i=1:numel(e_array)
    eqn12=([e_array{i}.F5].*cosd(theta))+(Fp2.*cosd(gamma))==F7x
    eqn13=([e_array{i}.F5].*sind(theta))+(Fp2.*sind(gamma))==F7y
    % do other calculations
end
Related Question