How do you randomize numbers but not have two consecutive numbers be the same?

I have 25 different tones (5 frequencies, 5 amplitudes in combination) and I need to play them in a randomized order, but I do not want any tones with the same frequency or amplitude to be next to each other.

my script plays the tones according to my currently randomized order for example:

column 1 corresponding to frequency (1-5 for the 5 different frequencies) and column 2 corresponding to amplitude (1-5 for the different amplitudes)

1  4
2  4
4  2
5  5
4  4
4  5
3  5
5  2
1  3
4  3
3  4
4  1
2  3
5  1
1  1
3  2
1  2
1  5
5  4
2  2
2  5
3  3
5  3
3  1
2  1

How can I edit my script so that no sounds of the same frequency or amplitude are played consecutively?

[Walter Roberson]

Play them in randomized order -- I take it that you mean that they are each to be played exactly once, but subject to those constraints?

[bym]

If you want them in a random order,couldn't that include the possibility that the same frequency and amplitude is played consecutively?

[Lisa]

Hi, I'm sorry the formatting of the numbers did not come out correctly. but yes, there should be 2 columns with 25 rows, each with a coordinate of (freq, amp). I have 25 different tones, 5 freq x 5 amplitudes, and I would like them to play in a randomized order each time, but not allowing tones of either the same freq or amplitude to be consecutive. so, im looking for a way to 'pseudorandomize' them

Answer 1

[Matt Fig]

Use the RANDPERM function. Depending on what you want to do, pick one of these:

>> A = [1 2;3 4;5 6;7 8;9 10]  % Sample Data
A =
     1     2
     3     4
     5     6
     7     8
     9    10
>> A(randperm(5),:) % Keep rows the same, but different order

ans =
     7     8
     9    10
     3     4
     1     2
     5     6
>> [A(randperm(5),1), A(randperm(5),2)] % Mix rows and cols separately
ans =
   3     8
   7     6
   5    10
   1     2
   9     4

Answer 2

[Paulo Silva]

function d=selpair(b,s)
%The input b is a column matrix with even values
%The input s is the number of pairs of values
%The output d is the a values but without being repeated
%by Paulo Silva
e=0;
for c=1:s
    d(c,:)=b(1+e,:);
    b(1+e,:)=[];e=0;
    while(isempty(b) | d(c,:)==b(1+e,:))
        e=e+1;
        if ((e>=(s-1)) | (numel(b(:,1))<2))
            return
        end
    end
end

To test the function use your data or this one

clc
clear
Pairs=25;
a=zeros(Pairs,2);
a(:,1)=round(0.5+abs(5*rand(Pairs,1)));
a(:,2)=round(0.5+abs(5*rand(Pairs,1)));
SortedData=selpair(a,Pairs);

[Lisa]

Hi, sorry, I am new to Matlab. Can you clarify what the selpair function is? Right now, I am using the following code to randomize my numbers

a=[1:5];

a=repmat(a,1,5);

a=sortrows(a');

b=[1:5];

b=repmat(b,1,5);

b=b';

c=[a b];

randqu=randperm(25)';

trial=randqu;

stimlist=[trial c];

mylist=sortrows(stimlist,1);

but this does not control for 2 tones of the same freq or amp being next to each other.

[Paulo Silva]

selpair filters your data, it should avoid the situations you don't want to happen like two consecutive rows same freq and amp :) I hope it works the right way for you :)

[Lisa]

When I try to use it, it says

Function definitions are not permitted in this context.

Do I need to have a file saved already in order to use this function?

[Paulo Silva]

Save the code of the function in one m file and use the other code to test it in the comand line or in other m file (this is the one you run)

[Lisa]

yes, i was able to get the function to work. thank you

however, the sorted data i got was:

4 4

3 4

4 2

1 5

5 5

3 2

5 1

2 2

5 1

4 4

3 5

5 4

5 5

4 4

4 3

3 5

5 3

4 4

1 2

1 4

2 4

5 3

2 4

1 2

4 1

is there a way for me to make sure no 2 consecutive tones have the same frequency OR amplitude? For example, in this data, the first 2 tones have the same amplitude. (freq = 1st column, amp=2nd column)

thank you for your help! it is much appreciated

[Paulo Silva]

I made the function to detect same freq and tone, it was my mistake, I will change the code to do what you want

Answer 3

[Paulo Silva]

Here's a better version, I included Matt Fig idea of the permutation, now my function can also randomize the rows of data and apply restrictions.

function d=selpair(b,at)
%The input at is the number of attempts that the function makes
%After the first attempt fails and if at>1 it will do a permutation of
%the rows of the data and try again, it will do permutations until all the
%data restrictions are satisfied or number attemps = at
%Made by Paulo Silva 25-01-2010

s=numel(b(:,1));
for atn=1:at
    b=b(randperm(s),:); %randomize the rows
    [d code]=selpairfind(b,s);
    if (code==1)
        break
    else
    %move the randperm line to this line if you don't want the data
    %to be randomized at the first attempt
    end
end

      function [d code]=selpairfind(b,s)
   %The input b is a (s,2) matrix
   %The input s is the number of tones
   %The output d is the matrix b but without consecutive rows with
   %the same freq or amp, other detections are included
   %just uncomment the line with the while you want and comment the others
   %The returned value might not have the same size as the input
   %(less lines), this is because the function can't satisfy the condition,
   %it happens in the end of the data.     
          e=0;
          for c=1:s
              d(c,:)=b(1+e,:);
              b(1+e,:)=[];e=0;
              %detect same freq
              %while((isempty(b)) | (d(c,1)==b(1+e,1)))
              %detect same amp
              %while((isempty(b)) | (d(c,2)==b(1+e,2)))
              %detect same freq and amp
              %while((isempty(b)) | (d(c,:)==b(1+e,:)))
              %detect same freq or amp
              while((isempty(b)) | ((d(c,1)==b(1+e,1))|(d(c,2)==b(1+e,2))))
                  e=e+1;
                  if ((e>=(numel(b(:,1))-1)) | (numel(b(:,1))<2))
   %Sometimes the function cannot satisfy the condition very near
   %the end of the data, some lines are ignore and the output size
   %is smaller than the input, if you wish the size to be always the
   %same just uncomment the next line (=no condition for that data)         
                      %d=[d;b];
                      if (isempty(b))
                          code=1;
                      else
                          code=0;
                      end
                      return
                  end
              end
          end
      end
  end

Code to test and compare the data

clc
clear
clf
Pairs=25;
at=10; %number of attempts
a=zeros(Pairs,2);
a(:,1)=round(0.5+abs(5*rand(Pairs,1)));
a(:,2)=round(0.5+abs(5*rand(Pairs,1)));
SortedData=selpair(a,Pairs,at);
subplot(211)
plot(a)
xlabel('Original data, the horizontal lines are repeated values')
legend('Freq','Amp')
subplot(212)
plot(SortedData)
xlabel('Filtered data')
legend('Freq','Amp')

Answer 4

[Bruno Luong]

Generate 100 pairs, no two consecutive pair has the same frequency OR the same amplitude:

% Data
f = (1:5)'
a = (1:5)'
Npairs = 100

% number of elements of f and a
nf = numel(f); % 5
na = numel(a); % 5

% Engine
indf = ceil((nf-1)*rand(Npairs,1)); % 0 excluded
indf = mod(cumsum(indf),nf)+1; % wrap around (0:nf)

inda = ceil((na-1)*rand(Npairs,1));
inda = mod(cumsum(inda),na)+1;

pairs = [f(indf) a(inda)] % two columns F and A

% Bruno

[Lisa]

This is the data I am generating:

4 3

1 2

3 5

2 3

5 5

2 3

5 2

4 3

2 1

3 5

1 1

2 4

4 3

1 4

3 1

4 4

1 3

2 4

1 2

4 5

1 4

5 2

1 4

4 2

3 3

I only want to play each tone once, and I also want to play every tone (5 freq x 5 amp = 25 unique tones). For example, in the above data in rows 2 and 19, the same tone is playing. I would like to play all 25 tones in a randomized order, with no two tones with the same freq or amp being consecutive. thanks

[Bruno Luong]

Challenging problem if all the pairs must be listed once. Note that the problem does not have solution for 2 x 2. Only from 3 x 2 or 2 x 3.

[Paulo Silva]

Lisa the last version of my code does exactly what you want? did you test it?

[Bruno Luong]

I haven't try your solution Paulo but to me it's a half satisfied solution. (1) The function merely attempt too rearrange an existing list without warranty the success. (2) It is not obvious whereas the (conditioning) permutations probability is uniform.

[Paulo Silva]

Bruno you are right and I can't come up with a better solution :(

[Matt Fig]

It should be pointed out, for clarity, that if the original row order is to be preserved, then only one of indf or inda is needed.

Answer 5

[Paulo Silva]

function d=selpair(b,s)
%The input a is a column matrix with even values
%The input s is the number of pairs of values
%The output f is the a values but without consecutive rows with 
%the same freq or amp
e=0;
for c=1:s
    d(c,:)=b(1+e,:);
    b(1+e,:)=[];e=0;
    while((isempty(b)) | ((d(c,1)==b(1+e,1))|(d(c,2)==b(1+e,2))))
        e=e+1;
        if ((e>=(s-1)) | (numel(b(:,1))<2))
            return
        end
    end
end

[Lisa]

thank you very much!!

[Walter Roberson]

Paulo, you could have just changed d(c,:)==b(1+e,:) to any(d(c,:)==b(1+e,:))

[Paulo Silva]

good catch Walter :)

Answer 6

[Paulo Silva]

function d=selpair(b,s)
%The input b is a (s,2) matrix
%The input s is the number of tones
%The output d is the matrix b but without consecutive rows with 
%the same freq or amp, other detections are included
%just uncomment the line with the while you want and comment the others
%The returned value might not have the same size as the input 
%(less lines), this is because the function can't satisfy the condition,   
%it happens in the end of the data.

e=0;
for c=1:s
  d(c,:)=b(1+e,:);
  b(1+e,:)=[];e=0;

    %detect same freq
    %while((isempty(b)) | (d(c,1)==b(1+e,1)))
    %detect same amp
    %while((isempty(b)) | (d(c,2)==b(1+e,2)))
    %detect same freq and amp
    %while((isempty(b)) | (d(c,:)==b(1+e,:)))
    %detect same freq or amp
    while((isempty(b)) | ((d(c,1)==b(1+e,1))|(d(c,2)==b(1+e,2))))
        e=e+1;
        if ((e>=(numel(b(:,1))-1)) | (numel(b(:,1))<2)) % * error fixed *
            %Sometimes the function cannot satisfy the condition very near
            %the end of the data, some lines are ignore and the output size
            %is smaller than the input, if you wish the size to be always the
            %same just uncomment the next line (=no condition for that data)
            %d=[d;b];
        return
        end
    end
end

Code to test and compare the data

clc
clear
clf
Pairs=25;
a=zeros(Pairs,2);
a(:,1)=round(0.5+abs(5*rand(Pairs,1)));
a(:,2)=round(0.5+abs(5*rand(Pairs,1)));
SortedData=selpair(a,Pairs);
subplot(211)
plot(a)
xlabel('Original data, the horizontal lines are repeated values')
legend('Freq','Amp')
subplot(212)
plot(SortedData)
xlabel('Filtered data')
legend('Freq','Amp')

Answer 7

[Paulo Silva]

Another implementation, please test it and report all possible errors

function d=selpair(b,at,Tdet,r1)
%The input at is the number of attempts that the function makes
%Tdet is the type of detection
%Tdet=1 detects same freq
%Tdet=2 detects same amp
%Tdet=3 detects same freq and amp
%Tdet=4 detects same freq or amp
%The input r1 enables the permutation of the data also in first attempt
%r1=1 yes do permutation at first
%r1~=1 no, try first without permutation
%it will do permutations until all the data restrictions are
%satisfied or number attemps = at
%Made by Paulo Silva 25-01-2010
s=numel(b(:,1));
for atn=1:at
    [d code bres]=selpairfind(b,s,Tdet);
    if (code==1)
        disp('Success, data returned with all conditions satisfied')
        break
    else
        if ((atn~=1) | ((r1==1) & (atn==1)))
            b=b(randperm(s),:); %randomize the rows
        end
    end
end
if (code==0)
disp('Failed to satisfy all conditions, try again with more attempts')
message=sprintf('The last %d lines dont satisfy the conditions',numel(bres(:,1)));
disp(message)
userchoice=input('Do you still want to include those lines? y/n ','s');
if (strcmp(userchoice,'y') | strcmp(userchoice,'yes'))
disp('Success, data returned with all conditions satisfied exept last lines')
d=[d;bres];
end
end

      function [d code b]=selpairfind(b,s,Tdet)
          %The input b is a (s,2) matrix
          %The input s is the number of tones
          %Tdet is the type of detection
          %Tdet=1 detects same freq
          %Tdet=2 detects same amp
          %Tdet=3 detects same freq and amp
          %Tdet=4 detects same freq or amp
          %The output d is the matrix b but without consecutive rows with
          %the same freq or amp, other detections are included
          %just uncomment the line with the while you want and comment the others
          %The returned value might not have the same size as the input
          %(less lines), this is because the function can't satisfy the condition,
          %it happens in the end of the data.
          e=0;
          for c=1:s
              d(c,:)=b(1+e,:);
              b(1+e,:)=[];e=0;
              if ((isempty(b)))
                  condwhile=1;
              else
                  if (Tdet==1)
                      %detect same freq
                      condwhile=((d(c,1)==b(1+e,1)));
                  end
                  if (Tdet==2)
                      %detect same amp
                      condwhile=((d(c,2)==b(1+e,2)));
                  end
                  if (Tdet==3)
                      %detect same freq and amp
                      condwhile=((d(c,:)==b(1+e,:)));
                  end
                  if (Tdet==4)
                      %detect same freq or amp
                      condwhile=(((d(c,1)==b(1+e,1))|(d(c,2)==b(1+e,2))));
                  end
              end
              while(condwhile)
                  e=e+1;
                  if ((e>=(numel(b(:,1))-1)) | (numel(b(:,1))<2))
                      if (isempty(b))
                          code=1;
                      else
                          code=0;
                      end
                      return
                  end
              end
          end
      end
  end

Answer 8

[J Richards]

Hi there,

Does anyone know of a way to stop elements from being repeated more than three times in a row? I have a 3 x 920 matrix consisting of the numbers 1 to 4, and wish to ensure that no number occurs more than 3 times consecutively in any column.

Thanks,

James

[Oleg Komarov]

Submit an independent question. You're more likely to get an answer.