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

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.

[Adam]

Unless you have created a cell array called randi I don't really see how you could get that error on that line.

[Nora Khaled]

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

[José-Luis]

 actOld{i}=randi(3);

If you actually want actOld to be a cell array.

[Adam]

Ah yes, for some reason I read the error message the wrong way round, converting from cell to double!

[Nora Khaled]

I want it to be an array because if I used actOld{i} there will be an error in line

[~,nUsers(k)]= length(find(act==k))

the error message "Undefined function 'eq' for input arguments of type 'cell'."

[José-Luis]

I could give you (what I think is) a solution for that, but that would just lead to you getting stuck somewhere else. Trying to guess what you are trying to achieve is wasting your and my time.

Instead of blindly forging ahead, I'd recommend you read the documentation on cell arrays so you understand what you are doing and see if there are better ways.

Maybe somebody else will, but for me, going through your code and fixing it for you is the definition of work. People tend to get paid for that.

Not offering my services, just ranting.

[Adam]

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]

thank you all.

Answer 1

[Fangjun Jiang]

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.

[Nora Khaled]

I want it to be an array because if I used actOld{i} then act(j) will be act{j} and there will be an error in line

[~,nUsers(k)]= length(find(act==k))

the error message "Undefined function 'eq' for input arguments of type 'cell'."

[Walter Roberson]

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]

thank you all.

Answer 2

[Jan]

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.

[Nora Khaled]

thank you.