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Formulation to Matlab code

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Maroco Sc
Maroco Sc on 14 May 2019
Answered: Steven Lord on 14 May 2019
How to write this formulation in Matlab:
2.JPG
is it :
for i=1:N
S(i) = -PT(i) * log(PT(i));
end
  2 Comments
Dimitris Kalogiros
Dimitris Kalogiros on 14 May 2019
What is the base of the logarithm? Is it 10 ? If so, then you must use log10() .
Maroco Sc
Maroco Sc on 14 May 2019
I have checked several papers, they did not mention the base of logarithm. if it is 10, then the code will be:
for i=1:N
S(i) = -PT(i) * log10(PT(i));
end
Right?

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Accepted Answer

Steven Lord
Steven Lord on 14 May 2019
There's no need to loop. The log and log10 functions can operate on arrays of data, and as long as you use element-wise multiplication you can do this in one line. [Actually, I'll need two; one to create sample data and one for the actual operation.]
PT = 10*rand(10);
S = -PT.*log10(PT);
You can compare this with the result of doing the same operation one element at a time to see if they're different.
S2 = zeros(size(PT));
for whichelement = 1:numel(PT)
S2(whichelement) = -PT(whichelement).*log10(PT(whichelement));
end
S-S2

More Answers (1)

Raj
Raj on 14 May 2019
Since your equation asks for 'log' not 'ln' , I think the code should be:
for i=1:N
S(i) = -PT(i) * log10(PT(i));
end

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