This error keeps popping up and I have no idea why: Error using viscircles Expected input number 1, centers, to be real. Error in viscircles​>validateC​entersAndR​adii (line 283) validateat​tributes(c​enters,{'n​umeric'},{​'nonsparse​','real', ... Erro

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Matthew Palermo
Matthew Palermo 2019-12-4
回答： Walter Roberson 2019-12-5
I am trying to do an animation for a linkage system and it is not plotting one of the links for some reason.
P1_pos = [56.25;43.1];
P2_pos = [56.25-A*cos(theta);43.1-A*sin(theta)];
P4_pos = C*[0;1];
P5_pos = D*[0*sin(theta);-1+1*sin(theta)]; %P5_pos = D*[0;-1+sin(theta)];
E = sqrt(A^2 + D^2 - 2*A*D*cos(theta));
a = asin(A*sin(theta)./E);
b = acos(E.^2 + C^2 - B^2)./(2*E*C);
P3_pos = [C + B*cos(a+b); B*sin(a+b)];
P5x = P5_pos(1,:);
P5y = P5_pos(:,1);
P5vx = diff(P5x);
P5vy = diff(P5y);
P5v = sqrt(P5vx.^2 + P5vy.^2);
ani = subplot(2,1,1);
P1_pos_cir = viscircles(P1_pos',0.05);
P2_pos_cir = viscircles(P2_pos(:,i)',0.05);
P3_pos_cir = viscircles(P3_pos(:,i)',0.05);
P4_pos_cir = viscircles(P4_pos',0.05);
P5_pos_cir = viscircles(P5_pos(:,i)',0.05);
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dpb
dpb 2019-12-4
Yeah, I noticed that too, but that's using i as an array index which would be another error on indexing must be real and positive...

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Walter Roberson
Walter Roberson 2019-12-5
You did not give us any values to test with for A, B, C, D
E = sqrt(A^2 + D^2 - 2*A*D*cos(theta));
Looks like the area of a triangle with sides A and D and angle theta between them. The area of a triangle is often greater than 1 but depending on the values of the variables could also be small < 1.
a = asin(A*sin(theta)./E);
A*sin(theta)./E can end up greater than 1, leading to asin() of a value greater than 1, which is complex valued. Everything gets messy from that point

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