Defining function handles in MATLAB
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How might I define a function handle?
For example, I want to define a function f(x)=2*x^3+7*x^2+x
I want MATLAB to evaluate f(x) at random values x. I have heard of feval and fhandles, but I don't know how to do it.
Thanks.
2 commentaires
Leia Sofia Mendez
le 26 Juil 2017
Modifié(e) : Walter Roberson
le 26 Juil 2017
This was the code I was trying to write:
a= 0.0009
a= convtime([1],'samples','seconds')
This code gave an error saying that my function (convtime) was undefined. How you define a function in MATLAB?
Walter Roberson
le 26 Juil 2017
Leia Sofia Mendez:
convtime appears to be from the File Exchange https://www.mathworks.com/matlabcentral/fileexchange/28204-time---rate-unit-conversion-function .
You should go to that link, and click the download button, and download the .zip file. You should unzip to a directory that is not under your MATLAB installation directory. You would then use pathtool in MATLAB to add that directory to your MATLAB path.
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Chandra Kurniawan
le 8 Jan 2012
Modifié(e) : MathWorks Support Team
le 22 Mai 2019
Hi, Richard.
To evaluate f(x) at different values of x, you can create an .m file and write this code:
function y = f(x)
y = 2 * (x^3) + 7 * (x^2) + x;
If you save the file under the name 'f.m', you can run the function by typing this code in the Command Window or a separate .m file.
x = randi(7);
y = f(x)
The randi function above generates a 1-by-5 row vector of random integers between 1 and 10. The values returned by f are stored in a 1-by-5 row vector y.
For more information about creating functions, see:
You can create a handle to the function f with an @ sign. For example, create a handle named myHandle as follows:
myHandle = @f;
Now you can run f indirectly by using its handle.
y = myHandle(x)
For more information about function handles, see:
5 commentaires
Plus de réponses (6)
Walter Roberson
le 8 Jan 2012
Function handle version:
f = @(x) 2*x^3+7*x^2+x;
Then f is already the function handle, and you can call f(3.7) (for example)
There is no need to use feval() for this, but you could.
1 commentaire
Salaheddin Hosseinzadeh
le 13 Mar 2014
I rather this anonymous way of defining a function! It's way easier. I also know another way of doing this, surprisingly nobudy mentioned that so far! lol I'm gonna put it in the answers.
Junaid
le 8 Jan 2012
Dear Richard,
To define a function in matlab you can do following syntax of given function:
function n = F(x)
n= 2*x^3+7*x^2+x;
that is it. You can put end at the end of function. But it is also acceptable not to put to various matlab versions. If you put end for one function then you have to put for all function in single m file.
then you can generate random numbers, either integer or double, and can get the values of this function.
cyril
le 21 Mar 2014
Modifié(e) : cyril
le 21 Mar 2014
> f = @(x) 2*x^3+7*x^2+x;
> f(0)
0
surprising no one mentioned anonymous functions...
1 commentaire
Salaheddin Hosseinzadeh
le 21 Mar 2014
@ Cyril
Walter did, just make sure you checked the other answers and comments!
samy youssef
le 11 Mar 2015
Modifié(e) : Walter Roberson
le 26 Sep 2016
here is a function i developed to calculate the log of any number with different base:
function d =log_for_diff_base(myNumber,myBase)
x=log(myNumber);
y=log(myBase);
d=x/y;
end
1 commentaire
Nikitha Challa
le 26 Sep 2016
x = x + a/x 2 in matlab code
2 commentaires
John D'Errico
le 26 Sep 2016
Modifié(e) : John D'Errico
le 26 Sep 2016
Not a function at all. This is not even valid MATLAB code as written.
Walter Roberson
le 26 Sep 2016
That does not appear to be a question, and it is not an Answer to what was asked here?
If the question is to solve the equation
x == x + a/(x^2)
then for finite a values, the solutions are -inf and +inf as a/(x^2) would be 0 for those values, leading to the equality -inf == -inf and +inf == +inf
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