To generate a Pseudorandom sequence based on some constraints

I have 4 base triplets- ABC, DEF, GHI, JKL. Also there are catch word- Z. I want a pseudorandomixed sequence generated such that: * a) Each triplet should be repeated 40 times * b)No repeated triplets should be present (e.g. …T1T1…) * c)No repeated pairs of triplets should be present (e.g. …T1T2T1T2…). * d)The catch should also be presented 40 times

Also can the code give me the transitional probability of first letter in each triplet? Eg. if a part of the random sequence is- ABC and DEF, what is the transitional (conditional) probability of D|C?

Can anyone help me do this?

Answer 1

[Matt J]

Here's one possibility. The transition probabilities are always 1/5, except for every 5th transition, which are 1/4

 function out =  myfunc(N)

   if nargin<1, N=40; end

   A=zeros(5,N);
   A(:,1)=randperm(5).';

   for ii=2:N

     A(1,ii)=randi(5);
     z=(1:5).';
     z(A(1,ii))=[];

     A(2:end,ii) =  z(randperm(4));

   end

   triplets={'ABC','DEF','GHI','JKL','Z'};

   out=reshape(triplets(A),1,[]);

[Pragati Rao]

Thanks Matt, What if I had to change the number of triplets? make it 6 triplets? and had to increase the number of repetition?

[Matt J]

Not a problem. Just change the 5s to 6s and so forth.

[Pragati Rao]

my abc, def triplets are actually music notes abc=C#, D#, E; def=F#, A, B; ghi=C,G#,A and jkl=D, G,F#. I used this code to generate them:

Fs=8000;
 Ts=1/Fs;
 t=[0:Ts:0.3];
 F_A = 440; %Frequency of note A is 440 Hz
 F_B = 493.88;
 F_Csharp = 554.37; 
 F_D = 587.33;
 F_E = 659.26;
 F_F = 698.5;
 F_G = 784.0;
 F_Dsharp=622.3;
 F_Fsharp = 739.9;
 F_Gsharp=830.6;
 F_C=523.3;

 trip_ABC=[F_Csharp;F_Dsharp;F_E];
 trip_DEF=[F_F;F_A;F_B];
 trip_GHI=[F_C;F_Gsharp;F_A];
 trip_JKL=[F_D; F_G; F_Fsharp];

 abc=cos(2*pi*trip_ABC*t); 
 def=cos(2*pi*trip_DEF*t); 
 ghi=cos(2*pi*trip_GHI*t);
 jkl=cos(2*pi*trip_JKL*t);

sig_abc = reshape(abc',3*length(t),1); 
sig_def = reshape(def',3*length(t),1);
sig_ghi = reshape(ghi',3*length(t),1);
sig_jkl = reshape(jkl',3*length(t),1);

my question is how do I now generate the same pseudorandom sequence (with notes instead of alphabets) with same constraints AND have outputs for the TP? i.e TP of first note of a triplet|last note of any of the remaining three triplets? eg TP F|E, TP F|A, TP F|F#.