anonymous, piecewise-defined function that has NaN as response for a certain subdomain

Question

Thomas Schäfer 2022-8-31

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评论： Thomas Schäfer 2022-9-1

I want to make an Matlab anonymous, piecewise-defined function that has NaN as response for a certain subdomain, but I am uncertain how to do this.

For an anonymous, piecewise-defined function without NaN response like this:

I would use a script like this:

g=@(x) (x) .* (x<=-1)+...
    (x+1) .* (x>-1 & x<1)+...
    (-x+4) .* (x>=1);

I would apriciate if someone would give me a tip how to include a subdomain that has NaN as response in my anonymous function, let say g(x)=NaN for 2<x<=4. I do not have access to any relevant toolboxes.

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Answer 1

Walter Roberson 2022-8-31

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... + 0./~(2<x & x<=4)

If the value is not in the range then the basic logic test returns false and ~ that is true which is 1 and 0./1 is 0 so 0 would be added which would have no effect.

If the value is in the range then the basic logic test returns true and ~ returns false which is 0 and 0./0 is nan.

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Thomas Schäfer 2022-9-1

yes, this works! Thanks!

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Answer 2

Torsten 2022-8-31

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在 MATLAB Online 中打开

g=@(x) (x) .* (x<=-1)+...
    (x+1) .* (x>-1 & x<1)+...
    (-x+4) .* (x>=1);
x = [-2,0,1.5,2.5,5];
gx = g(x);
gx(x>2 & x<=4)=NaN
gx = 1×5
   -2.0000    1.0000    2.5000       NaN   -1.0000