how can i declare a variable in a function for the first time only ,

function h=src(input)   %example
output=0  %here i won't output to be declared again when matlab gonna calcul src(input-1) 
if input==0
   output=output 
else 
  output= output +1 
  src(input-1)
end 

Answer 1

[Adam Danz]

I think this is what you're looking for,

function h=src(input)   
persistent output     %%%%%%%%
if isempty(output)          %%
    output = 0;             %%
end                   %%%%%%%%
if input==0
   %output=output;    % What's this ?? 
   % Do nothing
else 
  output= output + 1;
  src(input-1);
end 
h = output;           % assign output!

However, this still has problems.

1. What if user enters src(-1)? What about src(.9)? The input will never reach 0 and you'll run out of memory. To prevent the user from entering negative or non-scalar values, use an argument validation function.
2. You probably want to reset output back to 0 after input reaches 0. In that case, you can make this change,

if input==0
   %output=output;    % What's this ?? 
   h = output;
   output = 0; 
else ...

[sofiane benhamza]

it wasn't important to me , i'd just wrote it ,i thank you very mush but this code is my problem

it should computes the sum of digits of a positive number which is already given (ex: 12345=>1+2+3+4+5=15) , and it must containt recursive function, and i shouldn't worry about the input , but i couldn't understand , why it didn't

function h=src(input)           %input is already given
h=0;output=0;    %needed for calculations
if input == 0           %  0 gonna give 0
    Output=output ;
    s(Output)      %to display the Output in screen , 3rd function
    return
else
    f(input)          % to the second function
end
end
function z=f(input)
z=input*.1                                           %{ i'm trying to do it by this way ,
if input=214  , > z=214*.1=21.4 ,    a=(z-fix(z))*10=(21.4-21)*10 = 4
    t=0;                                                        t will contain the final result     t=t+a   this works if z~=fix(x) (case when
    a=0 , that's why i add if
    if z==fix(z)
        t=t+z;
    else
        a=(z-fix(z))*10;
        t=t+a;                                           %t should contain the final result
        Output=t;
        input=fix(z);
        src(input)                                 %return to the main function i there  is more numbre  21 will be 2.1 and like this
        t=t+1 ............;;t=t+2
    end
end
    function ss=s(k)              %this one is just to display the result if found  , but mt code still have problems and i
        can't find them
        ss=0;
        display(k)
    end

[Adam Danz]

So the input is 12345 or is it [1,2,3,4,5]?

[sofiane benhamza]

they said that it's one positive number , and i'm not allowed to use loops or str2num , i wish that it was a vector

[Adam Danz]

There are already lots of solutions for this within this forum.

Search the forum for phrases like

• Convert integer to vector
• Convert scalar to vector
• 123 to 1 2 3

etc...