Functions with 2 variables

How do you make a function (NOT an anonymous function) from this?

"Als" means "if"

Thanks in advance

[Rik]

Creating a function is fairly basic Matlab:

function output=MyFunction(input1,input2)

Is this what you mean? And why do you want to specifically avoid an anonymous function?

[Jens Petit-jean]

Thanks!

yeah, I need the function like you did, but I don't know how to programm this one because of the 2 variables x and k.

I don't want an anonymous function so I can use this function in other programms too.

Thanks in advance

[Rik]

Well, this function signature will do the trick. Did you do a basic Matlab tutorial? I can recommend Onramp.

[Jens Petit-jean]

thanks, but I already know how this works, I already did it with only one variable X but know I have 2 variables X and K and I can't find a way too program this function

[Walter Roberson]

k does not need to be an input for this function. The conditions have to do with x modulo 4: -2 <= mod(x,4) < 0 is the second condition, and 0 <= mod(x,4) < 2 is the first condition.

[Walter Roberson]

Duplicate of earlier https://www.mathworks.com/matlabcentral/answers/746957-how-to-program-a-function-with-2-variables?s_tid=srchtitle

Answer 1

[Walter Roberson]

format long g
mat2str(g(-9:.5:9))

ans = '[0 0.5 2 3.5 4 3.5 2 0.5 0 0.5 2 3.5 4 3.5 2 0.5 0 0.5 2 3.5 4 3.5 2 0.5 0 0.5 2 3.5 4 3.5 2 0.5 0 0.5 2 3.5 4]'

function output = g(x)
   k = floor(x/4);
   rm = x - 4*k;
   mask = rm < 2;
   output = zeros(size(x));
   output(mask) = 4-2*(rm(mask) - 1).^2;
   output(~mask) = 2*(rm(~mask) - 3).^2;
end

[Jens Petit-jean]

thanks!!

[Jens Petit-jean]

Why you do k=floor(x/4)

[Rik]

Can you guess based on what the purpose is? If you divide a number by 4 and round the result down, what have you effectively done?

[Jens Petit-jean]

i think because in the first inequality 4k <= x? But this does not apply to k in the other inequalities, does it?

[Rik]

If you would have to find the value for k with pen and paper, how would you do it?

And why would you expect two different values for k in the same expression? (in Matlab you need two separate operations for a<x<b (i.e. (a<x)&(x<b)), but mathematically that is a single expression)

[Walter Roberson]

k is an element of integers.

For any given real finite x, there is exactly one integer k such that 4*k-2 <= x < 4*k+2. If you try to use any other k then both range tests will fail.

Once you know the k that makes the above true, then the two different conditions decide between halves, 4*k-2 <= x < 4*k, or 4*k <= x < 4*k+2

I coded in a slightly tricky way for the second condition: you may need some study to figure it out.

I could have coded a different way overall, finding k based on floor((x+2)/4) . If you do that, make sure you get the boundaries right.

[Jens Petit-jean]

oooooh thanks I get it now, really appreciate the help!

Answer 2

[Asayel Alazmi]

Write an mfile using for loop to output a all numbers from 1 to 4 with an increment of 0.2

[Walter Roberson]

No, I don't think doing that would help solve the question that the person posted.