How to clear variable data but not remove the variable from workspace?

I want to remove the data from variable, meaning i want to empty the variables present in the workspace. I don't want to delete/remove the variables from the workspace.

[Stephen23]

Have you tried

V = [];

?

[Ajay Paudyal]

I have tried that but I have more than 1000 variables in workjspace. And the script I am working on creates different variables names with different run. So, it would be difficult use this V = []; So, I am looking for a command which is already there in matlab can do that for me.

[Stephen23]

"And the script I am working on creates different variables names with different run."

Your data are badly designed. Bad data design forces you into writing slow, complex, inefficient code.

Fix your code by using one array (e.g. ND numeric, cell array, structure array, table) and simply accessing it using neat and efficient indexing, etc. This is what experienced MATLAB users would do, and is what the MATAB documentation recommends.

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

For example, if you had used one simple cell array to store your data, then the solution would be just this:

C(:) = {[]};

Neat, simple, efficient code because of better data design. The twelve hours you have already wasted on this are a good illustration of why your current approach is not recommended: even simple tasks become difficult.

Answer 1

[Walter Roberson]

No command is offered for that purpose.

You could write a function that used whos() to find a list of variables, and assignin('caller') to write to the variable.

You might want to take advantage of empty() as in

evalin('caller', sprintf('%s = %s.empty;', VARIABLENAME, VARIABLECLASS) )

Or I guess you could

evalin('caller', sprintf('%s(:) = []', VARIABLENAME))

[Ajay Paudyal]

Thanks for your response. There are more than 1000 variables in workspace, so this method wouldn't be feasible.

[Walter Roberson]

Tested on a variety of variable types.

Note that this code does not preserve the fields of a struct.

function empty_all_variables
   vars = evalin('caller', 'whos');
   for K = 1 : length(vars)
       varname = vars(K).name;
       try
       evalin('caller', sprintf('%s = %s.empty;', varname, vars(K).class));
       catch
           try
               evalin('caller', sprintf('%s(:) = [];', varname));
           catch
              warning('Problems emptying variable: "%s"', varname);
           end
       end
   end
end

Answer 2

[Steven Lord]

What do you mean by "empty"? Do you want to delete all the elements, thus eliminating information about the size of the variable?

x = magic(4)
x(:) = []

Do you want to overwrite all the elements with some uniform value? If so depending on whether the data type of the variable support missing or not, if it supports scalar expansion:

x = magic(4)
y = int8(x)
x(:) = missing
y(:) = 0 % int8 doesn't support missing

Or related to that, if you want to change all of the size, the values, and potentially the type:

x = magic(4)
x = missing

Do you want to overwrite with noise?

x = magic(4)
x(:) = rand(1, numel(x))

Or do you have something else in mind?

[Ajay Paudyal]

I want to delete all the elements, thus eliminating information about the size of the variable. But there are more than 1000 variables in the workspace and the name is also changing with different "RUN", so looking for something can delete all the elements, thus eliminating information about the size of all the variables

[Steven Lord]

But there are more than 1000 variables in the workspace and the name is also changing with different "RUN",

That's a discouraged programming pattern. See that page and this one for explanations of why it's discouraged and alternatives you can use instead to reduce the number of variables that you need to create and manage.