# Math Help - Matlab roots help

1. ## Matlab roots help

I need help in generating 100 different polynomials of a certain degree and then finding the total number real roots. I know that I can generate a random polynomial of say degree 5 by typing

x=roots(rand([1 6]))
I also figured out the total number of real numbers by typing
size(x(imag(x)==0))
Can someone help me in writing a for loop for this?

2. Originally Posted by YankeesFan
I need help in generating 100 different polynomials of a certain degree and then finding the total number real roots. I know that I can generate a random polynomial of say degree 5 by typing

x=roots(rand([1 6]))
I also figured out the total number of real numbers by typing
size(x(imag(x)==0))
Can someone help me in writing a for loop for this?
x=roots(rand([1 6]))

will not generate the polynomials and roots you want as all the coefficients will be positive and so before you start you have no positive roots.

Try:

x=roots(rand([1 6]-0.5))

CB

3. Originally Posted by YankeesFan
I need help in generating 100 different polynomials of a certain degree and then finding the total number real roots. I know that I can generate a random polynomial of say degree 5 by typing

x=roots(rand([1 6]))
I also figured out the total number of real numbers by typing
size(x(imag(x)==0))
Can someone help me in writing a for loop for this?
Basic for loop structure is:

Code:
rv=zeros(1,100);
for idx=1:100

%code to do what you want

rv(idx)=...  ; % assign the idx-th element of the
% results vector to result for current
% loop trip
end
CB