MATLAB: Error on if loop

error

if 0<theta<180, x=C*A
else xx=CC*AA
end
Undefined function or variable 'A'.
Error in DynamicsProject (line 60)
if 0<theta<180, x=C*A

Best Answer

It is asking you to define variable ‘A’.

That aside, the if condition should be defined as:

if (0 < theta) & (theta < 180)

There is not enough information presented to allow a more detailed Answer.

There’s quite likely a more efficient way to do what you want to do, if we have the necessary information to help you do it.

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MATLAB: How to import .dat data

fid=fopen('yourfile.dat','r');
data=cell2mat(textscan(fid,'','CollectOutput',1,'CommentStyle','#'));
fid=fclose(fid);

looks like would do it. You'll end up w/ an array of double.

MATLAB: How can i use a “while” loop to automatically increment omega

I imagine by ‘omega’, you actually intend:

w=(2*pi/5);

A while loop is best used if you want to increment it and then test to see if a specific value meets a specific criterion, and stop the loop when it does.

If you just want to increment it over a range without testing, use a for loop instead.

I experimented with vectorising your code by making ‘omega’ a vector and using element-wise operations where I could. It works for some calculations, but it makes the ‘xx’ calculation impossible. A loop is likely the only way to go.

I could not run this because ‘C’ and ‘a’ are not defined. Correct that, then see if this works for you:

theta=120;
sign=(cosd (theta)/abs (cosd (theta)));
u=.8;
wv = linspace(0, (2*pi/5), 10);                          % Vector Of Values For ‘w’
R=1;
c=4.05/12;
H=18/12;
y=H-(R*sind(theta/2));
Md=50/32.2;
Id=(.5*Md*R^2);
Mp=75/32.2;
Mb=30/32.2;
alpha=0;
u=.8;
L=(6/12*R);
g=32.2;
for k1 = 1:length(wv)
    w = wv(k1);
    ax = (-R*w.^2)*cosd(theta);                             % Modified For Element-Wise Operations


    ab = (-R*w.^2*cosd(theta))-(R*w.^2*sind(theta));        % Modified For Element-Wise Operations
    ay = (-R*w.^2)*sind(theta);                             % Modified For Element-Wise Operations
      AA=[1 0 1 0 0 0 0 0 0; 0 1 0 1 0 0 0 0 0; 0 0 -R*sind(theta) R*cosd(theta) 0 0 0 0 0; 0 0 0 0 1 0 1 0 0; 0 0 0 0 0 1 0 1 0; 0 0 -1 0 -1 0 0 0 0; 0 0 -c 3*R -c -3*R 0 0 0; 0 0 0 0 0 0 0 0 0; 0 0 0 0 0 0 0 0 0];
      CC=[0 Md*g Id*alpha 0 Md*g Id*alpha Mp*ax Mp*ay+Mp*g Mb*g];
      xx=CC*AA;
      if (0<theta) & (theta<180), x{k1} = C*a;
      else xx{k1} = CC*AA
      end
  end

I left ‘x’ and ‘xx’ as cell arrays because I don’t know how large they are.

Best Answer

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