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

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whyamiincollege on 29 Apr 2019
Edited: madhan ravi on 12 May 2019
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.

gonzalo Mier on 29 Apr 2019
Edited: madhan ravi on 12 May 2019
I think you need here the function poly2sym:

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gonzalo Mier on 29 Apr 2019
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 on 29 Apr 2019
Thanks!
gonzalo Mier on 12 May 2019
Accept the answer if it worked for you! :)