Functions with 2 variables

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Jens Petit-jean 2021-2-17

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/747757-functions-with-2-variables

评论： Walter Roberson 2021-2-21

采纳的回答： Walter Roberson

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

"Als" means "if"

Thanks in advance

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Walter Roberson 2021-2-17

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 2021-2-19

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

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Walter Roberson 2021-2-17

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/747757-functions-with-2-variables#answer_625627

在 MATLAB Online 中打开

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

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Walter Roberson 2021-2-17

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 2021-2-17