Please help me implement the equations: Pij = (f(i,j))/(∑_(i=1)^M∑_(j=1)^N〖f(i,j)〗) and H = ─∑_(i=1)^M∑_(j=1)^NPijlog2Pij
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Can someone please explain how to implement these equations in MATLAB?
Pij = (f(i,j))/(∑_(i=1)^M∑_(j=1)^N〖f(i,j)〗)
H = ─∑_(i=1)^M∑_(j=1)^NPijlog2Pij
采纳的回答
Ahmed A. Selman
2013-3-31
It would be something like (provide your own functions for f, and set up the values of M and N),
clc;clear;close; % set up, clean up..
% start of Pij part: Pij = (f(i,j))/(∑_(i=1)^M∑_(j=1)^N〖f(i,j)〗)
M=...; N=...; % give values
function f=functionF(x,y)
% ... how to find f for x (x is imported i) and y (it is j )
end % function
Pij_single=zeros(M,N); P_of_J=zeros(1,M); % initialize P's
for i=1:M
for j=1:N
Pij_single(i,j)=functionF(i,j);
end
P_of_J(i)=sum(Pij_single(i,:));
end
Pij_sumOnly=sum(P_of_J); % it must be a single value
for i=1:M
for j=1:M
P(i,j)=functionF(i,j)./Pij_sumOnly;
end
end
% End of Pij part
% Start of H part: H = ─∑_(i=1)^M∑_(j=1)^NPijlog2Pij
clear P_single, P_of_J; % in case you need to save memory
H_of_J=zeros(1,M);Hij=zeros(N,M);
% Mark 1
% Note: if you need H = ─∑_(i=1)^M∑_(j=1)^NPijlog2Pij use the code in mark2.
% If you mean H = ─∑_(i=1)^(M-1)∑_(j=1)^(N-1)Pij*log2(Pij) use below:
H=entropy(Pij);
disp('H is: '); H
% Mark 2. Delete the lines below if not needed
for i=1:M;
for j=1:N
Hij(i,j)=P(i,j).*log2(P(i,j));
end
H_of_J(i)=sum(Hij(:,1));
end
H=-sum(H_of_J);
disp('H is: '); H
% End of the code. Double check initial indices of M, N please.
更多回答（1 个）
Image Analyst
2013-3-31
0 个投票
Try to construct a pair of nested for loops over i and j. See the getting started section if you don't know how to program in MATLAB yet. The latter formula is the entropy and there are functions for that, such as entropyfilt() in the Image Processing Toolbox.
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