Newbie question about table indexing,loops and logical arguments (should be easy)

Hello all,

Lets say I have a table with two variables. X contains either characters or various empty cells(,) like so: X = [A , , B , , , C ...] and Y contains a logical argument indicating if there are characters in X, like so: Y = [1 0 0 1 0 0 0 1 ...]. Now, I want to fill the empty cells in X for a new variable (Z) so the empty cells always contain the character in the cell above like so: Z = [A A A B B B B, C ...].

So far my code looks like this:

if table.Y == 1
 table.Z = table.X (so far so good)
else table.Z = ? (and Im stuck...

I need to tell Matlab "go one up above in X and assign that value in Z" something like:

 table.Z =  table.X(i-1)...

Any ideas?

Thanks all for your patience!

Answer 1

[Jos (10584)]

I am not sure how you store your data. Here is an example with a cell array

X = {'A','','','B','B','','C','C',''}
Y = [1 , 0, 0, 1 , 1 ,0 , 1 , 1 , 0] % you can do without this one

Z = cell(size(A)) 
lastidx = 1 ;
Z{1} = A{1}
for k=2:N
  if Y(k)==0, % you could use isempty(A{k}) here
    Z{k} = A{lastidx}
  else
    Z{k} = A{k}
    lastidx = k 
  end
end

Answer 2

[Stephen23]

There is no need to waste time with an ugly loop:

>> X = {'A','','','B','B','','C','C',''};
>> idx = ~cellfun('isempty',X);
>> tmp = X(idx);
>> X = tmp(cumsum(idx))
X = 
  'A'    'A'    'A'    'B'    'B'    'B'    'C'    'C'    'C'

Note that this code assumes that the first cell is not empty (otherwise it throws an error).