Randperm a completely different set of numbers each loop

I have randperm operating in a loop. Looking for a way to randperm a completely different set of numbers than the previous loop. Every other loop can share similar numbers, but consecutive loops cannot. I could brute force it and run a check to see if any of the new numbers were in the previous set (if so, run again, if not keep it) but maybe there is an easier way?

In otherwords, is there a way to have randperm exclude numbers from an array?

Thanks

Answer 1

[Jan]

Guillaume's method without setdiff is 10 times faster:

curset  = [];
fullset = 1:100;
for k = 1:1e4
   newset         = fullset;
   newset(curset) = [];
   curset         = newset(randperm(length(newset), 10));
end

Answer 2

[James Tursa]

If you mean the numbers can be the same but have to be in different spots, I suppose you could rotate the matching numbers to get the new set. E.g.,

% Setup
n = 10;  % Some length
r_new = zeros(1,n);

% Code to generate new non-repeating set
r_old = r_new;
f = 1;
while( numel(f) == 1 )
    r_new = randperm(n);
    f = find(r_new==r_old);
end
if( numel(f) ~= 0 )
    g = f([end,1:end-1]);
    r_new(f) = r_new(g);
end

Whether this is worth it vs just brute force generate a new set ... I don't know.

Answer 3

[Guillaume]

You can always setdiff your previous set from the set you pass to randperm:

currentset = [];
fullset = 1:100;
while true
   newset = setdiff(fullset, previousset);
   currentset = randperm(newset, 10);
   disp(currentset);
end

[Jan]

Typos fixed:

currentset = [];
fullset = 1:100;
while true
   newset     = setdiff(fullset, currentset);
   currentset = newset(randperm(length(newset), 10));
   disp(currentset);
end