Write a script that calculates the ​​user produced polynomial. The polynomial can be input until the user decides to terminate the program.

Hello,

I've been given an asignment in school and I'm a bit stuck with this task in the title.

Can anyone help me write the script because I don't know how to create a polynomial that is user decided and loop it at the same time?

Thanks in adwance.

[Matt J]

Once you've written something, we can help fix things. As a hint, the following would be one way to read in a vector of polynomial coefficients, e.g,

>> p = input('\nEnter polynomial coefficients: ')

Enter polynomial coefficients: [1,2,1]

p =

     1     2     1

[Ivan Roko Cavka]

Thanks for the tip Matt, but I don't understand how can I make an indipendant equasion based on the users input. For e.g.

p = input('\nEnter polynomial coefficients: ')

x = input ('\nEnter the x coefficient; ')

y = p*x

If I type it like this, the x multiplies each of the matrix components, but I want the input to be read as a polynomial like e.g. x^3 + x^2 - 1 , or any other variation based on the users input. And I guess I should be using a while loop with all this done?

I only know a way to do it if I know how many charachters will the user put in, and it's not very efficient.

Hope you'll help me get this thing done, cuz it's driving me crazy ;)

Answer 1

[Matt J]

If you have the Symbolic Math Toolbox and wish to manipulate the polynomials in symbolic form, you can use poly2sym,

>> p = input('\nEnter polynomial coefficients: ')

Enter polynomial coefficients: [1,1,0,-1]

p =

     1     1     0    -1

>> P=poly2sym(p)
 
P =
 
x^3 + x^2 - 1
 

However, that's often unnecessary. There are many Matlab commands that can analyze polynomials given only a vector representing their coefficients, e.g.,

>> roots(p)  %roots of the polynomial

ans =

  -0.8774 + 0.7449i
  -0.8774 - 0.7449i
   0.7549 + 0.0000i