How to solve Conversion to cell from double is not possible.

Question

Nora Khaled 2017-8-29

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评论： Nora Khaled 2017-8-30

I am trying to create an array named actOld using this code

for i=1:nPlayers
    uAve{i}=zeros(nRoads,1);
    actOld(i)=randi(3);
end

and the error message " Conversion to cell from double is not possible. , actOld(i)=randi(3);" appears.

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Nora Khaled 2017-8-29

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I didn't.

this is the whole code:

inertia=0.5; 
nPlayers=10; 
nRounds=10;
nRoads=3;
mycongestion=zeros(nRoads,1);
congustion=zeros(nRoads,1);
congestionPlus1=zeros(nRoads,1);
for i=1:nPlayers
    uAve{i}=zeros(nRoads,1);
    actOld(i)=randi(3);
end
for i=1:1:nRounds
   for j=1:nPlayers
       ran=rand(1);
       if(ran<inertia || i==1) 
          act(j)=actOld(j);
       else 
          [~,act(j)]=min(uAve{j});
          actOld(j)=act(j);
       end % end ran< inertia , else  
       disp(ran);
       disp(act(j));         
   end % end nPlayers.
     for k=1:nRoads
         [~,nUsers(k)]= length(find(act==k))
     end %end nRoads. 
     congustion= getCongestion(nUsers);
     fprintf(' A= %.0f min  B= %.0f min C= %.0f min',congustion(1),congustion(2),congustion(3)); 
     congestionPlus1= getCongestion(nUsers + 1); 
     for j=1:nPlayers 
         for k=1:1:nRoads
             if (act(j)==k)
                 myCongestion(k)=congustion(k); 
             else 
                 myCongestion(k)=congestionPlus1(k);
             end %ends act(j)==k , else.  
         end %end nRoads.
         uAve{j}=uAve{j}+(1/j+1)*(myCongestion' - uAve{j});
     end % ends nPlayers. 
  end % end nRounds

Adam 2017-8-29

Well I don't see how it is a cell array at the moment. It appears to be a numeric array that is sub-optimally growing in a loop.

Nora Khaled 2017-8-30

thank you all.

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Answer 1

Fangjun Jiang 2017-8-29

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编辑：Fangjun Jiang 2017-8-29

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Your variable actOld must be cell. Check it using class(actOld);

>> actOld=cell(5,1);
>> actOld(1)=randi(3)
Conversion to cell from double is not possible.

Use actOld{i}=randi(i) if that is what you want.

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Walter Roberson 2017-8-29

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If you need to be able to assign an entire vector to act(j) where j is a scalar, then you will need to create a new Vector object class and define appropriate indexing and mathematical operations for it. When you have act(j) with scalar j then that is notation for referring to a scalar.

If I recall correctly, someone put a vector class into the File Exchange.

find(act==k)

As you want act to be a vector of vectors, and as k is a scalar there will be no places where the vector act(j) is equal to the scalar k.

Nora Khaled 2017-8-30

thank you all.

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Answer 2

Jan 2017-8-29

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You do not need a vector class or a cell array. The problem can be solved with numerical arrays directly:

uAve   = zeros(nRoads, nPlayers);
actOld = randi(3, 3, nPlayers);

No need for a loop. Accessing the sub matrices works easy and efficient. So there is potential to simplify the code and fix the problem at the same time.