For loop question, switch loop question, don't know how to incorporate them together

function [ vowels ] = findVowels( charCell )
    string st = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    a = st[Random.Range(st.Length)];
    charCell = {a1, a2; a3, a4};

      switch vowles(letter)
      case {'a' 'e''i''o''u'}
            a = {'letter1','letter2';'letter3','letter4'};
          otherwise 
            disp a = []
      end

My answer:

function [ doy ] = calcDayOfYear( day, month, year )
% Day, month and year are integers corresponding to a given date 
%and day is that date's of the year

if doy = numDays*month
  if year = 'a leap year';
     if year./400 = 2n;
        disp('a leap year');
        elseif (year./100 = 2n;
        disp('not a leap year');
        elseif year./4 = 2n;
        disp('a leap year');
        else
        disp('not a leap year');
     end
     numDays = 29;
     else
     numDays = 28;     
end

switch lower(month)
    case {1 3 5 7 8 10 12}
        numDays = 31;
    case {4 6 9 11}
        numDays = 30;
    case {2}
        if year = [a leap year];
        numDays = 29;
        otherwise
        numDays = 28;
end

Totally have no idea how to incorporate them together, it is such a mess for my code too

Thanks a lot for whoever is answering my question.

[Rajesh Balagam]

Please rephrase your question specifying the location of the issue. Also explain the problem you are trying to solve and how you are approaching it.

[Walter Roberson]

See https://www.mathworks.com/matlabcentral/answers/361259-for-loops-questions#answer_285751 for an analysis of the first part.