Conditional function on matrix

Question

0 个投票

Hello,

This is a tough one to explain.

I am analysing a big chunk of data and now I have a equation defined by intervals.

Kd=1 for Kt<0.2
Kd=e for 0.2<=Kt<=1.09*c2
Kd=f for Kt>1.09*c2

Kt=rand(8784,89);
c2=ones(size(Kt))/2;
e=rand(size(Kt));
f=rand(size(Kt));

I've simplified it quite a bit, because it envolves other matrixes (all with the same size (8784,89)) on the conditions.

My question is, how to execute it? I've tried piecewise, but I'm stuck with the symbolic. I would need to get Kd as double.

Kd(Kt)=piecewise(Kt<0.2,1, 0.2<=Kt<=1.09*c2,10, Kt>1.09*c2,5);

I've tried with If and elseif but as far as I've seen it will only analyze the first element of the array to verify if the condition is true:

if Kt<0.2
    Kd=1;
elseif 0.2<=Kt<=1.09*c2
    Kd=e;
elseif Kt>1.09*c2
    Kd=f;
end

Other ideas or something I'm missing?

edit: edited after trying solution given by Matt J.

thanks.

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Answer 1

Matt J 2019-4-23

编辑：Matt J 2019-4-23

1 个投票

vals=[1,10,5];
Kd=vals(   discretize(Kt,[-inf,0.2,1.09*c2,+inf])   );

Matt J 2019-4-24

编辑：Matt J 2019-4-24

 Kd=ones(size(Kt));
 condition1 = Kt>=0.2 & Kt<=1.09*c2;
 condition2 = Kt>1.09*c2;
 
 Kd(condition1)=e(condition1);
 Kd(condition2)=f(condition2);