error:An array for multiple LHS assignment cannot contain expressions.

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Yi-Le Li
Yi-Le Li 2018-11-18
编辑： madhan ravi 2018-11-18
Error: File: Q7.m Line: 12 Column: 2
What does the error mean?
I'm using Matlab to solve Mechanism problems,and here is my code.
I'm pretty sure that it's not InverseRR's problem.I have used that function in other problems ,and it worked.
Hope that somebody who good at it could help me,please><
clc
clear
a1 = 15 ; a2 = 30 ; a3 = 20 ; a4 = 30 ; alpha = 30;
Xq = 50 ; Yq = 8 ; Xr = 70 ; Yr = 8;
dXa = 10 ; dYa = 0;
Xa = 20 ;Ya = a1 ;
I = 1;
BC = sqrt(a3^2 + a4^2 - 2 * a3 * a4 * cos(alpha)) ;
[(theta04),(theta02),dtheta4,dtheta2,ddtheta4,ddtheta2] = InverseRR(Xq,Yq,a3,a2,Xa,Ya,dXa,dYa,ddXa,ddYa,I);
theta2 = theta02 - 180;
theta4 = theta04 - alpha;
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Yi-Le Li
Yi-Le Li 2018-11-18
@Stephen Cobeldick
>> Q7
Error: File: Q7.m Line: 12 Column: 2
An array for multiple LHS assignment cannot contain expressions.

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采纳的回答

Bruno Luong
Bruno Luong 2018-11-18
编辑：Bruno Luong 2018-11-18
Remove the parenthesis
[theta04,theta02,dtheta4,dtheta2,ddtheta4,ddtheta2] = InverseRR...
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Bruno Luong
Bruno Luong 2018-11-18
it means you get the error! Parenthesis on LHS is not valid syntax so why you ask me the meaning?
Yi-Le Li
Yi-Le Li 2018-11-18
Oh!!Got it !! I'm a new matlab learner.
Thank you so much for helping me solve it !!

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更多回答（1 个）

madhan ravi
madhan ravi 2018-11-18
编辑：madhan ravi 2018-11-18
The problem in your code was you put comma ( , ) instead of semicolon ( ; )
Reason see mldivide
a1 = 15 ; a2 = 30 ; a3 = 20 ; a4 = 30 ; alpha = 30;
Xq = 50 ; Yq = 8 ; Xr = 70 ; Yr = 8;
dXa = 10 ; dYa = 0;
Xa = 20 ;Ya = a1 ;
I = 1;
ddXa=3; %fake data change it to your value
ddYa=5; %fake data change it to your value
BC = sqrt(a3^2 + a4^2 - 2 * a3 * a4 * cos(alpha)) ;
%|------||------|----error was here
[theta04,theta02,dtheta4,dtheta2,ddtheta4,ddtheta2] = InverseRR(Xq,Yq,a3,a2,Xa,Ya,dXa,dYa,ddXa,ddYa,I);
theta2 = theta02 - 180;
theta4 = theta04 - alpha;
function[PHI,PSI,dPHI,dPSI,ddPHI,ddPSI] = InverseRR(Xq,Yq,c,b,Xa,Ya,dXa,dYa,ddXa,ddYa,I)
X = Xa - Xq;
Y = Ya - Yq;
A = 2 * c* Y;
B = 2 * c * X;
C = X^2 + Y^2 + c^2 - b^2;
t1 = (A + sqrt(A^2+B^2-C^2))/(C+B);
t2 = (A - sqrt(A^2+B^2-C^2))/(C+B);
if (I == 1)
t = t1;
else
t = t2;
end
PHI = 2*atan(t);
U = (X- c*cos(PHI))/b;
V = (Y- c*sin(PHI))/b;
PSI = atan2(V,U);
Xb = c*cos(PHI);
Yb = c*sin(PHI);
%%% Inverse Velocity%%%
dX = dXa;
dY = dYa;
D = [ -c * sin(PHI) -b * sin(PSI); c * cos(PHI) b * cos(PSI) ];
% ^--------- error was here
E = [ dX;
dY ];
F = D \ E ;
dPHI = F(1,1);
dPSI = F(2,1);
%%% Inverse Acceleration %%%
ddX = ddXa;
ddY = ddYa;
G = [ -c * sin(PHI) -b * sin(PSI); %error was here
c * cos(PHI) b * cos(PSI) ];
H = [ ddX + c * cos(PHI) * dPHI ^2 - b * cos(PSI) * dPSI ^2 ; %error was here
ddY + c * cos(PHI) * dPHI ^2 - b * sin(PSI) * dPSI ^2 ] ;
I = G \ H;
ddPHI = I(1,1);
ddPSI = I(2,1);
PHI = PHI / pi * 180;
PSI = PSI / pi * 180;
end

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