different operations for same string

lets say i have a string (string=('aBcdEf')). how do i make something like that?

output1= function on A to C (upper and lower case)

and

output2=function on D to F(upper and lower case)

Thank you

[dpb]

What does "function on (letter set)" mean, precisely?

It's simple enough to find the set members, the Q? is what is supposed to happen?

Give an example of expected outputs desired.

[Elie Elias]

For the characters in the first half of the alphabet ('A' to 'M' and 'a' to 'm'), convert them to the characters:

• A position further in the ASCII table if the difference between the ASCII code of the current character and the next prime number is odd.
• Two positions further in the ASCII table if the difference between the ASCII code of the current character and the next prime number is even.

Sorry if the question isnt clear, i google translated it from french

[Elie Elias]

basically this i what i have to do but i dont know how to do an operation on the characters A to M in one string

[madhan ravi]

Just give an example of your required output

[Image Analyst]

Clear as mud. When you say "the next prime number"? What is the current prime number? And as you know, the only even prime number is 2, so the next prime number being even would only be if the CURRENT prime number is 1, but we don't even know how you're obtaining any of these these prime numbers.

Try to read this link

Answer 1

[dpb]

Sounds pretty French to me! :)

function s=strfutz(s)
  % futz with characters in string
  % generate the test prime set
  %P=primes(200);P=P(find(P<'A',1,'last'):find(P>'z',1));
  P=[61 67 71 73 79 83 89 97 101 103 107 109 113 127];

    isOdd=@(x) logical(mod(x,2));  % convenient shorthand
    isEven=@(x) ~isOdd(x);

    u=upper(s);
    ix=ismember(u,'A':'M');   % first group
    ix=find(ix);              % absolute address in string
    io=isOdd(interp1(P,P,double(s(ix)),'next')-s(ix));
    ifix=ix(io);              % pick the odd ones out
    s(ifix)=s(ifix)+1;        % and increment the ASCII code 
    ie=~io;                   % even aren't odd
    ifix=ix(ie);              % pick the even ones now
    s(ifix)=s(ifix)+2;        % and increment the ASCII code 
  end

Some of the intermediaries could be fold together, but I believe this does what your description asks for.