How to generate a function from x-y vectors?

Question

Ajay Goyal 2017-2-6

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评论： Ghenam Dahmane 2022-3-4

Hello MATLAB users. I got two vectors (say x and y). Is there any way to create a function i.e. y=f(x). I do not want the expression. I just want to create the function in matlab for further calculations. For ease: x=[1 5 0 32 8]; y=[10 1 654 32 100];

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the cyclist 2017-2-6

Your question is not clear. What does "use these vectors in function form" mean?

Do you mean you want to find a function f(x) that will (approximately?) fit the x-y data? If so, what type of function? A polynomial?

Ajay Goyal 2017-2-6

编辑：Ajay Goyal 2017-2-6

If I do not get expression; its ok. I just want to create a funtion from these vectors so that further calculations like Fourier series etc can be done

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Answer 1

Nicolas Schmit 2017-9-4

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在 MATLAB Online 中打开

You question is not very clear, so I will try to guess what you are trying to do.

If you want to define a purely symbolic function f(x), use the following syntax.

syms f(x)

If you want to create a function from data points x and y, use the griddedInterpolant function to create a interpolation of x and y.

x=[1 5 0 32 8];
y=[10 1 654 32 100];
[~, index] = sort(x);
F = griddedInterpolant(x(index), y(index));

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Ajay Goyal 2017-9-4

Thank You, Nicolas Schmit

Ghenam Dahmane 2022-3-4

Thank you for your help Nicolas Schmit

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Answer 2

Yifan Ma 2018-2-6

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What you are looking for is map container. https://de.mathworks.com/help/matlab/ref/containers.map-class.html

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Answer 3

Luca 2020-3-31

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编辑：Luca 2020-3-31

Hi,

I have 2 vector (x, y) and I desire math expression y=f(x)

x must be syms. How to?

tnks

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Ajay Goyal 2020-3-31

编辑：Ajay Goyal 2020-3-31

Hi,

As much I did understood your query, you wish to establish relation as y=f(x) and values of x are not known. To answer, I believe, it is not possible as the values of x and y is the first necessity to develop a function. Then only you may use it to predict y for input values of x.

Contrary, if you just want to define a function, you may do it following way:

%%%%Main File:

syms x

[ y ] = Untitled2( x )

%%%%Function file:

function [ y ] = Untitled2( x ) %%%%same name as in main file. Func. file will be stored with this name

y=x.^2; %%%%wrtite the function. Say

end

Kindly let me know, if your query has been resolved.

Best Luck

Ajay

Ajay Goyal 2020-3-31