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Function, input number, return a value

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Eric 2015 年 4 月 29 日
コメント済み: Eric 2015 年 4 月 29 日
Write a small function which takes as inputs; a number a and a function g(x), and returns (a, g(a)). Note that printing is not the same as returning a value. Use the function g(x) = 2x 2 and a = 4 to test your function.
So my function right now looks like this.
function [a g(x)] = mysmallfunction(x)
a = x;
g(x) = 2*x.^2;
And I'm calling it like this:
[a g(x)] = mysmallfunction(4)
I get the error "Undefined function or variable 'mysmallfunction'."
But also I'm using a specific equation in 2x^2. How do I make it work for any equation.

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Guillaume 2015 年 4 月 29 日
編集済み: Guillaume 2015 年 4 月 29 日
Your tutor must have taught you about function handles for you to solve this problem.
As per the question, the function you have to write takes two inputs, a number and a function (see function handles) and returns two outputs, the original number and another number. Therefore you must have two variable names before the = in your function declaration and two variable names in the brackets of your function declaration.
Note that g(x) is not a valid variable name.
To get you started, the following declaration would work:
function [a, ga] = mysmallfunction(x, g)

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Eric 2015 年 4 月 29 日
I'm a little confused.
Are you saying you have to include the function(2x^2) inside the function itself and not when I call the function?
Aren't I suppose to insert the equation when I call the function? Otherwise wouldn't I have to keep on changing the equation(everytime I want to use a different one) in mysmallfunction.m file?
Guillaume 2015 年 4 月 29 日
No, you do not include the declaration of the function handle inside your own function, the function handle is one of the argument you pass to your function. That is, to test your function you would call it with
[a, ga] = mysmallfunction(4, @(x) 2*x^2);
Or to be more explicit:
g = @(x) 2*x^2
[a, ga] = mysmallfunction(4, g);
You only need to work out how to use the function handle inside your own function. I've shown you how in my previous comment.
Eric 2015 年 4 月 29 日
Aha! Thankyou I finally pieced all your hints together! Appreciate it


その他の回答 (1 件)

Pratik Bajaria
Pratik Bajaria 2015 年 4 月 29 日
You just have to change a few things and it must work. Atleast it does for me. ;-) you need not write g(x) literally.
function [a g] = mysmallfunction(x)
a = x;
g = 2*x.^2;
Call it like this:
[a g] = mysmallfunction(4)
Check and let me know if it works for you. I assume, i have got your problem right.
Regards, Pratik

  2 件のコメント

Guillaume 2015 年 4 月 29 日
I don't think you've got it right. The question clearly states that the function has two inputs.
Guillaume 2015 年 4 月 29 日
Eric's comment moved here:
Yes there is two inputs.
Pratik your solution would work for a defined equation.



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