How do I use a vector to evaluate a polynomial function?

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Josh
Josh 2013-2-16
I have a vector of x values that I need to plug into a cubic polynomial. And I keep getting errors
how exactly do I do this? The function is a polynomial and I keep getting errors
??? Undefined function or variable 'y'.
Error in ==> at 21 f(x)=y
OR
??? Error using ==> mpower Inputs must be a scalar and a square matrix.
Error in ==> @(x)x^3-2*x^2-3*x+1
Error in ==> at 21 y=feval(f,x) >>

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回答（1 个）

Shashank Prasanna
Shashank Prasanna 2013-2-16
You haven't show us how you are calling this function, that would give this question more clarity. In any case if you are calling the function with a vector input you will have to use the "." (dot) notation as below
x = rand(10,1); % some random numbers
f = @(x)x.^2 - 2*x.^2-3*x+1
y = f(x);
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Shashank Prasanna
Shashank Prasanna 2013-2-16
Josh, please share the exact implementation of your function, it will be easier to assist you if the above doesn't work.

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