I have to declare 6 variables with the constraint 0<=a1<b1<c​1<a2<b2<c2​<=255. How to do it? please help.

I have to declare 6 variables with the constraint 0<=a1<b1<c1<a2<b2<c2<=255. How to do it? please help. If possible please provide the code. Thanks in advance.

[Azzi Abdelmalek]

What do you mean by < I have to declare 6 variables> ?

[Walter Roberson]

Is this a question about using the Symbolic Toolbox and adding "assume" conditions?

Answer 1

[Azzi Abdelmalek]

You can check using this test

test=0<=a1 & a1<b1 & b1<c1 & c1<a2 & a2<b2 & b2<c2 & c2<=255

[Shramana GS]

Thanks for your reply. But the solution didnt work. I need to initialize these 6 variables randomly satisfying the constraint 0<=a1<b1<c1<a2<b2<c2<=255. Plz help.

[Walter Roberson]

Would 0<a1<b1<c1<a2<b2<c2<255 be okay? The equality conditions at the end are a bit tricky to handle while maintaining uniform random distribution.

val6 = {};
while length(val6) < 6
  val6 = num2cell( unique(rand(1,6)*255) );
end
[a1, b1, c1, a2, b2, c2] = val6{:};

The above will never equal exactly 0, or exactly 255, but can take on nearly any representable value in-between.

The equality constraints are not bad to handle if you are looking for integer values instead of floating point:

val6 = {};
while length(va6) < 6
   val6 = num2cell( unique(randi([0 255], 1, 6)) );
end
[a1, b1, c1, a2, b2, c2] = val6{:};

[Shramana GS]

Thanks for the suggestion. It worked. :) .

Answer 2

[Matt J]

If you mean you just want to generate 6 variables satisfying those bounds, this is one of many things you can do.

x=num2cell(cumsum(rand(1,6))*255/6);

[a1,b1,c1,a2,b2,c2]=deal(x{:});

[Jos (10584)]

Note that this will not produce random values for the variables:

x = cumsum(rand(6,10000))*255/6) ;
histogram(x(:),0:10:255)

[Matt J]

Jos, I think you mean that the variables will be random, but not uniformly distributed. That's fine. The OP made no such requirement, or really any specific requirements at all.

However, if uniformity were required, I would have proposed using RANDFIXEDSUM

   z=randfixedsum(6,1,rand,0,1);

   x=num2cell(  cumsum(z)*255 );

   [a1,b1,c1,a2,b2,c2]=deal(x{:});