Input a certain value into a symbolic matrix

Question

0 个投票

In advance, sorry for my English. The problem is that my M matrix is a symbolic matrix containing variable 'w' I simple want to input a certain number in the M matrix instead of the variable 'w' Here's my clumsy MATLAB code. I hope somebody can help me.

%========================================================================

L=1; K1=100000; Kt1=50000; K2=2000; Kt2=1000; E=0.26e10; q=7800; 
b=0.05; h=0.01; 
area=b*h; I=b*h^3/12; 
a=(q*area*w^2/(E*I))^(1/4); 
Q(x)=A*sin(a*x)+B*cos(a*x)+C*sinh(a*x)+D*cosh(a*x); %Q(x) 
d1Q(x)=diff(Q(x)); %Q(x)' 
d2Q(x)=diff(d1Q(x)); %Q(x)'' 
d3Q(x)=diff(d2Q(x)); %Q(x)''' 
d4Q(x)=diff(d3Q(x)); %Q(x)'''' 
Q_0=Q(0); d1Q_0=d1Q(0); d2Q_0=d2Q(0); d3Q_0=d3Q(0); d4Q_0=d4Q(0); 
Q_L=Q(L); d1Q_L=d1Q(L); d2Q_L=d2Q(L); d3Q_L=d3Q(L); d4Q_L=d4Q(L); 
BC1=d3Q_0-Q_0*K1/(E*I); 
BC2=Kt1*d1Q_0/(E*I)-d2Q_0 ;
BC3=K2*Q_L/(E*I)-d3Q_L ;
BC4=d2Q_L+Kt2*d1Q_L/(E*I) ;
M1=equationsToMatrix(BC1==0,[A,B,C,D]) ;
M2=equationsToMatrix(BC2==0,[A,B,C,D]) ;
M3=equationsToMatrix(BC3==0,[A,B,C,D]) ;
M4=equationsToMatrix(BC4==0,[A,B,C,D]) ;
M=[M1;M2;M3;M4];    % This is the M matrix containing variable 'w'
i=1;j=1;
for w=0:0.05:3000    % I set the value w, but it does not go into the M matrix. 
    y(i)=w;
    dm(i)=det(M);
        if ((i>=2) && ((dm(i-1)*dm(i))<0))
          f(j)=(y(i-1)+y(i))/2;
          j=j+1
      end % decide whether the w value makes the M determinant passing 0, if yes, this is the nature frequency
      i=i+1;
  end