I keep getting this : "The following error occurred converting from sym to double: Unable to convert expression into double array."

This is my code for the Routh criterion , but ,as the title states, i keep getting error in line 13 : b(i) = e(2*i). I tried to fix the code using others users' suggestions but it still doesn't work. Thank you in advance.

function [k] = routhc(pol)
syms x 
k = sym('k');
c = coeffs(pol,x);
e = fliplr(c);
l=length(e);
m=mod(l,2);
if m==0
    a=rand(1,(l/2));
    b=rand(1,(l/2));
    for i=1:(l/2)
        a(i)=e((2*i)-1);
        b(i)=e(2*i);
    end
else
    e1=[e 0];
    a=rand(1,((l+1)/2));
    b=[rand(1,((l-1)/2)),0];
    for i=1:((l+1)/2)
        a(i)=e1((2*i)-1);
        b(i)=e1(2*i);
    end
end

%%now we generate the remaining rows of routh matrix
l1=length(a);
c=zeros(l,l1);
c(1,:)=a;
c(2,:)=b;
for m=3:l
    for n=1:l1-1
        c(m,n)=-(1/c(m-1,1))*det([c((m-2),1) c((m-2),(n+1));c((m-1),1) c((m-1),(n+1))]);
    end
end
disp('the routh matrix:');
disp(c);
%%now we check the stablity of system
%syms k
kvalue = solve(c(:,1)>0,k,'ReturnConditions',true);
k = kvalue.conditions
end

Answer 1

[Harsha Priya Daggubati]

Hi,

I tried executing the above code using the following polynomial '16*x^2 + 19*x + 11'. Your code executed with no errors, giving the following Routh matrix as a result.

>> routhc(16*x^2 + 19*x + 11)
the routh matrix:
    16    11
    19     0
    11     0

 
k =
 
symtrue
 
 
ans =
 
symtrue

Could you provide me with the polynomial you are working with, so I can reproduce the same.