How to count occurrences of a letter?

The question is as follows: a. Your job is to write a function called CrazyGrade that will take in the string and flip the grades according to the following specifications: A becomes F B becomes D C remains unchanged D becomes B F becomes A Y becomes W Your function should take in a string as an input argument and return the inverted string as an output argument. You may assume that the input string will only consist of valid letter grades.

b. * To make matters worse, he wants you to tell him his grade distribution. So write a second function GradeDist to return the number of A's, B's, etc. So if there are 4 A's, 16 B's, 18 C's, 10 D's, 4 F's, and 3 W's, your function should return [4 16 18 10 4 3].*

I am working on part b but cannot figure out how to count the occurences with what I have so far. my code so far looks as follows:

clc,clear

oldgrade=input('Enter letter grades (without spaces in between) ','s');

x=sscanf(oldgrade, '%c'); for i=1 : length(x)

    switch x(i) 
        case {'a','A'} 
            grade = 'F'; 
        case {'b','B'}                  
            grade = 'D';
        case {'c','C'}
            grade = 'C';
        case {'d','D'}
            grade = 'B';
        case {'f','F'}
            grade = 'A';
        case {'y','Y'}
            grade = 'W';
    end
      fprintf('%s %s,', grade)
end

Answer 1

[Henrik]

A quick and dirty solution could be

F_count=0;
switch x(i) 
      case {'a','A'} 
          grade = 'F'; 
          F_count=F_count+1;

etc.

There are probably much more efficient solutions, though.

Answer 2

[Star Strider]

The histc function is your friend for the second part. Note that it takes alphanumeric inputs for both the data and the bin ranges.