MATLAB Function Finds The Derivative and Evaluates at Point A
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My task is to write a MATLAB function that calculates the derivate of a polynomial, represented in vector form, and then also evaluates the derivative at a point a. So far I have the code to find the derivative, I just do not know how to evaluate at a from there. Note: f(x) = 3x^4 - 5x^2 -6x can be represented as P = [3, 0, -5, -6, 0]. Here is what I have so far:
function [PP,PPa] = ex5(P,a)
%
% where PP = the derivative of P
% PPa = the derivative of P evaluated at a
n = length(P);
PP = (n-1:-1:1).*P(1:n-1);
PPa = %not sure what to put here
4 个评论
Steven Lord
2020-12-9
If I gave you a polynomial like
and asked you to evaluate it (by hand, with pencil and paper) at x = 4 how would you do that? List the steps, not just the answer. Can you adapt your pencil and paper technique into MATLAB code and use it to evaluate p = [1 2 3] at x = 4;?
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/456334/image.png)
Use polyval not as part of your implementation but to check your answer during development, comparing the result of your code to the results from polyval.
回答(1 个)
James Tursa
2020-12-9
移动:Sabin
2023-1-15
@Sophie: You might investigate the .^ operator (element-wise raise-to-power).
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