Finding average length of elements in a cell array

In my code I am sorting through a collection of tweets. I have separated out the handles (ex: @Handle) by using the following code.

FID = fopen('Tweets.txt');
Line = fgetl(FID);
while ischar(Line)
    %Finds total amount of handles in the tweets%
    Handles={};
    FileContents = fileread('Tweets.txt');
    Handles = length(regexp(FileContents, '@'));  
    for h = 1;size(Handles);
        HandlesString = num2str(Handles);
        RegHandles = regexp(HandlesString, '(#)\w+','match');
    end
    if regexp(Line, '@')>1;
       %I
       %Displays all Handles in a CELL ARRAY%
       HandlesNum = HandlesNum+1;
       RegHandles2 = regexp(Line, '(@)\w*', 'match');
       CharHandles = char(RegHandles2);
       NumHandles = str2num(Char);
       HandlesCell = cell(RegHandles2);
       disp(HandlesCell)
    end
    Numbers = [Numbers; Num];    
    Line = fgetl(FID);
end

What I am now attempting to do is to find the average (mean) length of all the handles in the file. How could I go about this process?