MATLAB: How to save a matrix that is set within a loop

loop

I use a loop to select certain rows from a matrix, satisfying the condition that the element in de first column of the row should be equal to 140,141,…,148.
w(1) starts at 140, so in de first time in the loop, the rows from the matrix are selected that have the element in the first column equal to 140. This happens 9 times, repeating for the other values of w.
I would like to store each "selection" from the matrix that is made in a matrix. I saw other similar questions but none of them helped me to solve this specific case.
 M=9; 
 i=1;
 w(1)=140;   %select from frame 140
 for m=1:M   %to frame 148
      w(m+1)=w(m)+i;
      Info=allInfo((allInfo(:,1)==w(m)),:)
 end
I hope someone can help me! Thanks in advance.

Best Answer

I would use accumarray, which makes this quick and efficient to implement:
>> M = randi([140,150],100,10); % Fake data matrix
>> V = 140:148; % the values that you want
>> X = 1:numel(V);
>> fun = @(v){M(M(:,1)==v,:)};
>> out = accumarray(X(:),V(:),[],fun); % the output
For example the first cell contains the rows matching V(1), the last one contains the rows matching V(end):
>> out{1}
ans =
   140   145   148   145   147   150   141   149   146   150
   140   146   142   148   149   146   140   145   143   142
   140   140   144   142   141   146   141   146   144   149
   140   144   140   140   144   146   142   147   145   141
   140   142   148   142   147   145   145   146   146   140
   140   150   146   147   149   150   147   140   148   148
   140   144   142   142   145   144   144   149   142   143
   140   150   141   147   146   144   140   148   142   147
   140   144   140   143   142   146   143   149   141   145
   140   146   142   145   145   148   141   142   148   149
>> out{end}
ans =
   148   149   146   148   147   140   144   145   143   142
   148   140   144   148   145   140   142   145   146   149
   148   150   143   149   140   146   147   149   147   147
   148   142   144   146   144   149   150   145   142   143
   148   149   148   146   149   141   141   144   147   150
   148   146   144   149   141   145   150   141   143   148
   148   142   140   149   141   144   149   148   140   146
   148   148   142   141   145   150   148   149   142   150
   148   146   150   149   141   149   144   147   145   150
   148   150   147   147   144   149   145   143   145   148
Whatever you do, do NOT try to write slow ugly hack code that creates those matrices using dynamic variables: https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval
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