use diff for jacobian but there is a problem

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seonghun kim 2018-5-6

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https://ww2.mathworks.cn/matlabcentral/answers/399334-use-diff-for-jacobian-but-there-is-a-problem

评论： Star Strider 2018-5-6

syms x y z theta; a=90; b=122; t=50; v=[x y theta];

L1=sqrt(((-a/2*cosd(theta)-((b+t)*sind(theta))+x+1000).^2)+(-a/2*sind(theta)+(b+t)*cosd(theta)+y-1072).^2); Lx=diff(L1,x) Ly=diff(L1,y) Ltheta=diff(L1,theta)

L2=sqrt(((a/2*cosd(theta)-(b+t)*sind(theta)+x-1000).^2)+(a/2*sind(theta)+(b+t)*cosd(theta)+y-1072.)^2); Lx2=diff(L2,x) Ly2=diff(L2,y) Ltheta2=diff(L2,theta)

L3=sqrt(((b+t)*sind(theta)-x).^2+((1072-(b+t)*cosd(theta)-y).^2)+(1100+a/2).^2); Lx3=diff(L3,x) Ly3=diff(L3,y) Ltheta3=diff(L3,theta)

x=(-20:0.5:20); y=(-40:40); theta=(-40:40);

J=[Lx Ly Ltheta;Lx2 Ly2 Ltheta2;Lx2 Ly2 Ltheta3] J=det(A)

%the error is 함수 'cosd'은(는) 'sym'형 입력 인수에 대해 정의되지 않았습니다. function 'cosd' is not defined as inputted factor 'syms'

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Ameer Hamza 2018-5-6

在 MATLAB Online 中打开

I just ran your code and it is working fine. Can you run this line

which cosd

to see if this is problem with MATLAB paths.

seonghun kim 2018-5-6

it doesn't work ㅠㅠ expressed same error

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回答（1 个）

Siyu Guo 2018-5-6

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I think MATLAB does not recognize the function "cosd" in its symbolic computations. You should instead use "cos", which means you need to convert your x value from degrees to rads. When you substitute the symbolic variable x with some specific values, make sure the values are in rads rather than degrees. For example, replace the "cosd" and "sind" in your code with "cos" and "sin", and use "theta = deg2rad(-40:40)" rather than "theta = -40:40" to evaluate the expressions.