Can you find the error in this code that aims to sum the digits of a string?

I wrote this code in order to sum the digits of any string, and to also create a loop that stops the summing process when the length of the sum is equal to a single digit.

What's wrong?

n = '12361927'

function d = sumdigits(n)
  s=0
  for i=1:length(n)
    s=s+str2double(n(i))
  end
end

s=sumdigits(n)
if length(str2num(s))==1
  s=s
else
  while length(str2num(s))~=1
 
    
    if length(str2num(s))==1
      break
    else
      s=sumdigits(s)
      end
  end
  end

Answer 1

[Stephen23]

Simpler:

str = '12361927'
while numel(str)>1
    num = sum(str-'0')
    str = num2str(num)
end

Prints this in the command window:

str = 12361927
num =  31
str = 31
num =  4
str = 4

[GEORGIOS BEKAS]

sum(str-'0')?

[Stephen23]

str-'0'

subtracts the character code for '0' (which is 48) from the character codes of the character array str. If all of the characters in str are digits then it converts the chracter representation of those digits into their numeric values, e.g.:

>> '1234'-'0'
ans =
   1   2   3   4

[Stephan]

nice new knowledge

Answer 2

[Stephan]

Hi,

try :

n = '12361927'
s=num2str(sumdigits(n))

if strlength(s)==1
  s=s;
  disp('here')
else
  while strlength(s)~=1  
    if strlength(s)==1
      break
    else
      s=num2str(sumdigits(s))
      end
  end
end

function d = sumdigits(n)
  s=0;
  for i=1:length(n)
    s=s+str2double(n(i));
  end
  d=s;
end