how to define a variable used one time in function

if i have a function with a variable x=1 defined in side that function and the variable is increased by a formula and that function is called many times from another function , the question is how can make that variable x defined in side the function is set only at the first call and after the other calls it will not effect or set to 1 again , or in another meaning how to define a variable used one time in function , please do not tell me to define x=1 out of function body because the program that i worked on not allowed .

for example :

Function ABC()

x=1;

x=x+Pi;

end

Answer 1

[Mischa Kim]

ALAA, you can define x to be a global variable. Alternatively, you could use

 function xnew = ABC(x)
 ...
 xnew = x + Pi;
 end

to return the new value of x to the calling function.

[Maria]

Dear Mischa Many thanks

actually the main function had not called from any other function , actually I am working on simulink/matlab and the function is in function block (s-function ) and that function connected with robot model so it outputs variables to the model , actually i want to make random obstacles defined inside function block but the obstacles returned to their first location after the first feedback between model and function because i defined first obstacles locations in side function then i moved them randomly by rand(), so after second call they return to first locations due to first definitions of their locations inside function , so any suggestion

Ex:

function t=ABC ()

obstacle= [2 4];

obstacle(1)=obstacle(1)+rand() * 0.02; obstacle(2)=obstacle(2)+rand() * 0.03;

Answer 2

[Walter Roberson]

persistent x
if isempty(x); x = 1; else; x = x + 1; end