strings operations, how long is string, changing specific strings

I have a variable "F" where i have 6-7 charcters , now my questions are:

• 1 how i can cheack how long is this string?
• 2 now if it have 7 characters then i want to:
• for characters in position 1-3 if charcter=0 chacnge it into O , and for position 3-7 if charcter=O change it into 0,
• how can i do that?

Answer 1

[Stephen23]

Try this:

F = '000OOOO';
if numel(F)==7
    F(1:3) = strrep(F(1:3),'0','O');
    F(4:7) = strrep(F(4:7),'O','0');
end

I assumed that you meant your second range to start from 4.