plotting root of Polynomial Equation

hi , I'm trying to plot a root of polynomial equation that have to set of complex solution as 1 X 4 cell

any suggestion how to plot the data obtianed

p = [0.20,0.23,0.25,0.27]';

er1 = (1+1.8*10^14*i);

er2 = (2.5+2.5*10^-3*i);

pol = [2+p*0, (-2+3*p)*er2 + (1-3*p)*er1, -er1*er2+p*0];

EQ2 = arrayfun(@(i) roots(pol(i,:)),1:numel(p),'uni',0);

plot(p,EQ2)

[John D'Errico]

Note that the roots will not necessarily be in any special order. So when you do plot them in sequence with p, things may jump around.

One idea would be to convert the sequence of polynomials to a sequence of 4x4 matrices. This is called the companion matrix. you can find that in the function compan.

help compan

Then use my eigenshuffle utility (found on the file exchange) to resort the eigenvalues to be in a consistent order.

Finally, do as Star suggests, and plot the real part on the x axis, and the imaginary part on the y axis.

Answer 1

[Star Strider]

You need to extract the double arrays from the cells in ‘EQ’:

plot(p,real([EQ2{:}]),'-',  p,imag([EQ2{:}]),'--')

The cell2mat function is also an option.

[Ammar Ahmed]

thanks it working perfectly fine

[Star Strider]

As always, my pleasure.