How do I create a matlab function using polyder that not only gives the coefficients but also gives the equation

My code so far (doesnt work):

function derivativecoefficient  = derivpolycalc()
a = input('Enter the coefficent of the polynomial')
x == x
n = input('Enter the power of each x')
derivativecoefficient = polyder(a)
derivative = derivativecoefficient*x^(n - 1)
end

If i just do it where it shows the coeeficents, I could simply do:

function derivativecoefficient  = derivpolycalc()
a = input('Enter the coefficent of the polynomial')
derivativecoefficient = polyder(a)
>> derivpolycalc
Enter the coefficent of the polynomial[3,2,5]
a =
     3     2     5
derivativecoefficient =
     6     2
ans =
     6     2

BUT I want a code that will display

6x^2+2x+0..

or maybe it could display

6x^5+2x^3+0

depending on what the original function was.

Answer 1

[gonzalo Mier]

I think you need here the function poly2sym:

https://www.mathworks.com/help/symbolic/poly2sym.html

[whyamiincollege]

I'm not sure how I would do this?

[gonzalo Mier]

As easy as:

p = poly2sym(derivativecoefficient)

For 6x^2+2x+0 solution, you need derivativecoefficient to be [6 2 0], meanwhile if you need the solution 6x^5+2x^3+0, it will be [6 0 2 0 0 0].

Each value correspont to a coefficient of the full polynomial, and the ones that are nulls are equal to 0

[whyamiincollege]

Thanks!

[gonzalo Mier]

Accept the answer if it worked for you! :)