# Transition Matrix that compares two elements to the next two elements.

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Ellie on 27 Jul 2015
Commented: Walter Roberson on 28 Jul 2015
Hi all, I am trying to modify this code to create a transition matrix that compares two elements to the next two elements. As of now the code successfully compares two elements to the next one element. I have been trying to modify it, but have not had any luck. Any help would be greatly appreciated. Thanks.
close all
clc
dataset = [1 2 1 1 1 2 2 2 1 1 1 2 2];
precision = 1;
markovChain = (round(dataset/precision)).*precision;
%number of states
Nstates = max(markovChain);
%get Norder-contiguous sequences of the markov chain
ngrams = [];
for i = 0:1
ngrams = [ngrams, circshift(markovChain,[0 -1*(i)])'];
end
ngrams = cellstr(num2str( ngrams));
ngrams = ngrams(1:end-2);
%create all combinations of Norder-contiguous sequences
[x{1:2}] = ndgrid(1:Nstates);
%format x to cell
evalStr = ['xCell = cellstr(num2str(['];
for i = 1:2
evalStr = [evalStr 'x{' num2str(i) '}(:) '];
end
evalStr = [evalStr ']));'];
eval(evalStr);
%map ngrams to numbers
[gn,~,g]=unique([xCell;ngrams]);
s1 = g(Nstates^2+1:end);
%states following the ngrams
s2 = markovChain(3:end);
%get transition matrix
tm = full(sparse(s1,s2,1,Nstates^2,Nstates^2) );
transitionMatrix = bsxfun(@rdivide, tm, sum(tm,2));
Walter Roberson on 28 Jul 2015
I have given a solution in http://uk.mathworks.com/matlabcentral/answers/231381-error-using-accumarray-third-input-sz-must-be-a-full-row-vector-with-one-element-for-each-column-of to the form of the question presented there, which does not use those messy eval().

Azzi Abdelmalek on 27 Jul 2015
Edited: Azzi Abdelmalek on 27 Jul 2015
a=[1 2 1 1 1 2 2 2 1 1 1 2 2];
b=[0 1 0 0; 0.5 0 0 0.5; 1 0 0 0; 0.5 0 0.5 0];
state=[1 1;1 2;2 1;2 2];
q=zeros(4);
for k=1:4
for p=1:4
q(p,k)=numel(strfind(a,[state(k,:) state(p,:)]));
end
q(:,k)=q(:,k)/sum(q(:,k));
end
q
The result
q =
0 0.5000 1.0000 0.5000
0.5000 0 0 0
0 0 0 0.5000
0.5000 0.5000 0 0