Why do I keep on getting "Not Enough Inputs" for an If statement in a function

Hello, I keep on getting these two errors in my Matlab code

 >>PartOne
Please enter a number between 0 & 9999: 
42

num =

    42

Not enough input arguments.

Error in Big (line 6)

if (num <10000 )

Error in PartOne (line 11)

sum = (Big - Small);

>>

Heres my script code:

    num = input ( 'Please enter a number between 0 & 9999: \n' )
count =0;
sum = num;
converge = false;
while num >= 0 & num <= 10000  %Postive value between 1 and 4 digits.
for I=1:1:8
  count =+ 1 ;
  toBig = Big(sum);
  toSmall = Small(sum);
  sum = (Big - Small);
  
  if sum==6174
      converge = true;
      break;
  end
end
end

if converge
    fprintf(' %f Converges and needs %f iterations', num ,count )
    
elseif converge == false
    fprintf(' %f does not converge.', num)
end

And my function codes:

function SmB = Big(num) 
%Small to big

NUMARR= zeros(1,4);

if (num <10000 )

    Fourth = mod(num,10);
    Third = ( mod(num,100) - (mod(num,10)))/10;
    Second = ( mod(num,1000) - (mod(num,100)) )/100;
    First = ( mod(num,10000) - (mod(num,1000)) )/1000;
    
elseif (num<1000) % 3 digit number
    First = 0;
    Fourth = mod(num,10);
    Third = ( mod(num,100) - (mod(num,10)))/10;
    Second = ( mod(num,1000) - (mod(num,100)) )/100;
    
elseif( num<100) %2 digit 
    First = 0;
    Second = 0;
    Fourth = mod(num,10);
    Third = ( mod(num,100) - (mod(num,10)))/10;
   
elseif (num<10) %1 digit
  First = 0;
  Second = 0;
  Third = 0;
  Fourth = mod(num,10);
  
end

   NUMARR(1,1) = First;
   NUMARR(1,2) = Second;
   NUMARR(1,3) = Third;
   NUMARR(1,4) = Fourth;
   
  sort(NUMARR);
 
  SmB = (NUMARR(1,1)*1000) + (NUMARR(1,2)*100) + (NUMARR(1,3)*10) + (NUMARR(1,4)) ;

end

function BiS = Small(num) 
%Big to Small

NUMARR= zeros(1,4);

if num<(10000) %4 Digit Number

    Fourth = mod(num,10);
    Third = ( mod(num,100) - (mod(num,10)))/10;
    Second = ( mod(num,1000) - (mod(num,100)) )/100;
    First = ( mod(num,10000) - (mod(num,1000)) )/1000;
    
elseif (num<1000) % 3 digit number
    First = 0;
    Fourth = mod(num,10);
    Third = ( mod(num,100) - (mod(num,10)))/10;
    Second = ( mod(num,1000) - (mod(num,100)) )/100;
    
elseif (num<100) %2 digit 
    First = 0;
    Second = 0;
    Fourth = mod(num,10);
    Third = ( mod(num,100) - (mod(num,10)))/10;
   
elseif (num<10) %1 digit
  First = 0;
  Second = 0;
  Third = 0;
  Fourth = mod(num,10);
  
end

   NUMARR(1,1) = First;
   NUMARR(1,2) = Second;
   NUMARR(1,3) = Third;
   NUMARR(1,4) = Fourth;
   
  sort(NUMARR, 'descend');
 
  BiS = (NUMARR(1,1)*1000) + (NUMARR(1,2)*100) + (NUMARR(1,3)*10) + (NUMARR(1,4)) ;
   

end

Answer 1

[Adam Danz]

'Big' is a function. When you call this line

  sum = (Big - Small); 

you're calling your function Big() without any inputs. The same is true for 'Small()'.

You haven't provided the 'Big' function but that's probably what's going on assuming it's similar to the Small() function.

By the way, your variable names need some work. "Sum" should never be a variable name since the sum() function is a common function. In generaly, variable names and function names should be descriptive.