MATLAB: Selectivly remove values from a matrix with a loop

error handlingforloop

I wrote a program that takes data from different databases and plots them. However, sometimes one or more of the databases inputting data yields no values from a query.
When this happens, I get an error message,
'index exceeds matrix dimensions'
Right now, my guess on how to solve this is to run a 'for' loop. (I want to remove the null set of data from a data array as well as a 'names' array (for the plot legend))
I have n data sets and a names array with n names.
I want to do:
for i=1:n %Check each database
     if dataarray{i}=0  
%If the data is null (This might not be the right way to do this...but basically if there IS data...it is stored as a 350x2 double array...and if there is NOT data...its stored as 0 (a double array I believe)
            delete ith value from dataarray 
             %I dont know how to do this
            delete ith value from namesarray
             %Also dont know how to do this
             n=n-1 
             %For plotting in the future..we have one less dataset..now n-1 datasets
end
end
So thats what I am trying to accomplish. I have been trying to read about error handling from matlab, and have also browsed this forum, but cannot find exactly what I need.
Any help would be great!

Best Answer

It looks like you are using a cell array.
dataarray = {9, [8 8;9 9], 7, 0, [5 9], 0, magic(2), 0, 'string'}
dataarray = dataarray(~cellfun(@(x) isequal(x,0),dataarray))
The reason why you should not use a FOR loop for this is that you set the loop to iterate over the original length of the variable. Then if you delete a value in the variable, the length of the variable decreases, but the loop will keep right on going. Here is a simple example to follow:
A = [1 2 3 4];
for ii = 1:length(A)  % ii is going to 4, unless an error occurs...
   ii  % Display current value of ii
   A(ii) = []  % What will happen when ii is 3??
end
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