Assign an empty table

Hi,

I am trying to assign an empty table (lets say "groupData" to be used later in the for loop. In the loop I use another table and fill the groupData. Later on I would like to empty the table (groupData) and refill again and so. I tried the following code , did not work.

I got the error o convert a table to numeric, use the TABLE2ARRAY function. Is there a way to assign an empty table without using table2array, because I use the groupData data after the for loop to get the data with their variable names. Like

 if (groupData.Node(i)==4000)&& (groupData.Cell(i+1)==11)

Thank you

Birsen

Here is the code

==============

for h=1:3

      k=newK;
      m=1;
       groupData(:,:)=0

      while pData.Node(k)~=4000
          groupData(m,:)=pData(k,:)
          k=k+1;
          m=m+1;
      end
  newK=k+1;
  end

Answer 1

[Birsen]

I think I resolved it as follows:

groupData = array2table(zeros(0,9));

groupData.Properties.VariableNames = {'Node','x2', ...
           'x3','Cell', 'x5','x6','x7', 'x8', 'x9'}

Just defining groupData = array2table(zeros(0,9)) was not sufficient. I had to also use

groupData.Properties.VariableNames = {'Node','x2', ...
           'x3','Cell', 'x5','x6','x7', 'x8', 'x9'}

[Joseph Transom]

That is not an empty table. It is a table of zeroes. Zero and empty are very different things.

The only 'empty' table MATLAB can create, is 0x0. To check this, create a table T of non-zero dimestions: just give it a size and some variable names and types.

It will be populated with zeroes for the numeric datatypes, and non-empty cells containing an empty double for cells.

Test varfun(@isempty,Z,'Outputformat','uniform') - you will get a logical array indicating false.

[Walter Roberson]

>> groupData = array2table(zeros(0,9))

groupData =

0x9 empty table

MATLAB believes that it is an empty table.

I think you failed to note that the first parameter to zeros is 0, which causes a variable with no rows to be created. Remember that a variable is considered empty if any of its dimensions is 0.

[Amos]

... as a single statement + alternative zero-height array syntax

groupData = array2table( double.empty(0,9) ...
                       , 'VariableNames' ...
                       , {'Node','x2','x3','Cell', 'x5','x6','x7', 'x8', 'x9'} ...
                       )

Answer 2

[Walter Roberson]

If the idea is that you want to write 0 over top of all of the existing entries, then

groupData{:,:} = 0;

If you want to remove all of the entries, then

groupData(:,:) = [];

[Birsen]

Walter thank you for the answer. But both gave an error I tried groupData{:,:} , got the following error "The following error occurred converting from table to cell: Conversion to cell from table is not possible".

And tried groupData(:,:) = []; got error too. "Deletion requires an existing variable".

[Walter Roberson]

>> groupData = array2table(rand(5,2))
groupData =
  5×2 table
          Var1                 Var2       
    _________________    _________________
    0.929021451353742    0.945085903751417
    0.723183836546625    0.705712522061558
    0.346528149686704    0.801252732520179
    0.453861726186205    0.680579929444058
    0.993489506713988    0.784894685163496
>> groupData{:,:} = 0;
>> groupData
groupData =
  5×2 table
    Var1    Var2
    ____    ____
    0       0   
    0       0   
    0       0   
    0       0   
    0       0