How to find undefined matrix in a code?

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Hello everyone, i have a matrix that presents the alarmed devices in the coverage of an access point , but i dont have alarmed devices for all access point covarege area, and you know at that time the matrix for alarm is undefined, totally empty matrix so i can't use it in the following steps. What i am asking is : is there any way to write an if statement saying if that matrix is defined do that, if it is undefined do another thing. Can you help me please?

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James Tursa
James Tursa il 3 Mar 2015
If the variable is not defined at all, you can use this:
if( exist('variable_name','var') )
% variable_name is defined
% variable_name is not defined
If the variable is in fact defined but is actually empty, do this instead:
if( isempty(variable_name) )
% variable_name is empty
% variable_name is not empty
  2 Commenti
Cladio Andrea
Cladio Andrea il 3 Mar 2015
Just perfect , the second one actually is what i want. Thank you so much !!
Guillaume il 3 Mar 2015
In that case, for reference, the matrix is actually defined (i.e. the variable has been declared). The proper term is that it is empty (hence why you use isempty).

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