How to define a string variable in IF statement

I'm stuck with matlab on almost every simple step I used to work with pretty fast in PHP. How this piece of code inside my function makes me crazy:

matchStr = regexp(filename,'^([0-9\-])+-StockAndOptionQuoteFor([A-z]+)\.', 'tokens');
CurDate = matchStr{1,1}{1,1};
if(~Ticker)
    Ticker = matchStr{1,1}{1,2};
end

Matlab keeps telling "Undefined function or variable 'Ticker'." or The variable 'Ticker' might be used before it is defined! But it's a standard practice in PHP. How do I know which type of variable it would be, a string or double?

Ticker='' didn't help

Answer 1

[Andrei Makarskiy]

global Ticker; 
Inside the Function helped. But after the function stops running the global Ticker returns to '' in the workspace. I'm stuck.

[Star Strider]

Using global variables is not considered good programming practice, and can cause problems. Add the variable to the function argument list instead.

Answer 2

[the cyclist]

Spoiler alert: Different languages have different syntax. :-)

Are you trying to check if a variable named "Ticker" exists, and then create it if it does not? Then use the exist function

if ~exist('Ticker','var')
  Ticker = matchStr{1,1}{1,2};
end

In MATLAB, "~" means logical negation.

[Andrei Makarskiy]

Thanks, Folks. Your advice helped. Moreover, I found the problem which set the Ticker to '' every time I called the function, since the statement global Ticker; reset the variable to empty. So, I took out this piece of code to a more appropriate place outside the function.

[the cyclist]

This is an example of Star Strider's comment about defining global variables being a generally bad practice. Debugging problems can be a challenge, because code that is "far away" and difficult to find can affect something local.