MATLAB:

Write a function called diff_day that takes four scalar positive integer inputs, month1, day1, month2, day2. These represents the birthdays of two children who were born in 2015. The function returns a positive integer scalar that is equal to the difference between the ages of the two children in days. Make sure to check that there are 4 input values and each of them are of correct types and they represent valid dates. If they are erroneous, return -1. You are not allowed to use the built-in function datenum or datetime. WHAT IS WRONG WITH THIS!!

function dd = day_diff(month1,day1,month2,day2)

if validDate(month1,day1) && validDate(month2,day2)

dd = abs(covertToDays(month1,day1) - convertToDays(month2,day2));

else

dd = -1;

end

end

function val = validDate(m,d)

if ~isscalar(m)||~isscalar(d)||m<1||d<1||m~=fix(m)||d~=fix(d)

val=0;

else

switch m

case {1,3,5,7,8,10,12}

val=d<=32;

case 2

val=d<=30;

case {4,6,9,11}

val=d <= 30;

end

end

end

function days = covertToDays(month,day)

year= [31 28 31 30 31 30 31 31 30 31 30 31];

days = sum(year(1:month-1))+ day;

end