swapping two vector's elements in matlab - arrays

Question

I have two vectors, v1 (1x9) and v2 (1x4).
I have to write a function with two inputs, (x,y) and output of out.
x should be the index number x in v1.
y should be the index number y in v2.
The function should replace the xth element in v2 with the ythelement in v1 and give the new v2 as output.
As an example:
v1=[1 2 3 4 5 6 7 8 9];
v2=[1 2 3 4];
out = myfun(7,2);
then the output should be
out = [1 7 3 4];
The next time if x=9 and y=1
out = myfun(9,1);
out = [9 7 3 4];
my main program idea is
[M Z]=test(A,q)
A is matrix (mxn)
q is vector of length m
i=[1:m];j=[1:n];
c(:,j)=q./A(:,j);
find minimum element in c . as example it is c(I,j) then
x=I; and y=j;g
i = [1:x-1,x+1:m]; j = [1:y-1,y+1:n]; % starting new calculations
statements…calculation procedures to find matrix M instead of A and vector Z instead of q.
end of program
now I want to write myfunction which you did before inside this program
elseif v(x) <= v1(n) this program must working continuously (holding M and Z as new A and q in input and get the minimum ratio and so the new x and y ) until v(x)==n break
please help

Answer 1

You can save the variable and load it in the next call.
function v2 = myfun(x,y)
v1=[1 2 3 4 5 6 7 8 9];
v2=[1 2 3 4];
if exist('v2.mat', 'file' ) ~= 0
load('v2')
end
v2(y) = v1(x);
save('v2','v2');
end
You could also use persistant variable,
function out = myfun(x,y)
persistent v
if isempty(v)
v = [1 2 3 4];
end
v1=[1 2 3 4 5 6 7 8 9];
v(y) = v1(x);
out = v;
end
Note
mlock command locks the currently running function in memory so that subsequent clear functions do not remove it. Locking a function in memory also prevents any persistent variables defined in the file from getting reinitialized.
Edit
I got this form your comments, see how it goes,
function out = test(x,y)
persistent v
if isempty(v)
v = [1 2 3 4];
end
v1 = [1 2 3 4 5 6 7 8 9];
v(y) = v1(x);
if x == 3;
out = v;
return
elseif v(y) <= v1(9)
statements
end
out = v;
end