How can I make a set of numbers and add numbers to it later?

I want to create a set of numbers, like for example all odd numbers divisible by 3: S = {3, 9, 15} etc. I have thought of creating a vector, but in the calculation matlab doesn't see a vector as a set of numbers. Later on in my calculation I want to add even more numbers to the set S, for example I want to add the numbers {21, 27}. I have no clue how to fix this in matlab, the only thing I thought of was, as I said, creating a vector but that option doesn't seem to work for me. After creating a set of numbers I want to pick the elements out of the set and check whether they are divisible by 6 for example. But as soon as I know how to make such a set, my expectation is that picking some element out of it would be a matter of trial and error.

Is there an option in matlab to create a set of self chosen numbers, and add later even more numbers to the same set and make some more calculations with the expanded set after all? Thanks in advance.

[Azzi Abdelmalek]

I think you can make your question more clear and breve. For example, what do you mean by: matlab doesn't see a vector as a set of numbers. Give a short example and show what are you expecting as result.

[Maik Petersen]

Thanks for your comment. I want to make a set of numbers, with the help of a script.

I want to start with the set {2}.

Inside the forloop there has to be a conditional statement which checks whether each single number of the set is an even number, so

if ceil('number of the set'/2) == floor('number of the set'/2)
"action"
end

I want to check that for every number in the set, so using a vector would be ineffective.

Every loop that comes afterwards has to add a number to the set, so after 1 iteration the set should be {2,3}.

This is as concrete as I could go, I hope you understand me better now.

Answer 1

[Matt J]

Is there an option in matlab to create a set of self chosen numbers, and add later even more numbers

Yes, you just use a vector to represent your set and then concatenate more numbers to it, e.g.,

>> numset=[1 5 8 3],  expanded=[numset, [4 100,7]]

numset =

       1     5     8     3

expanded =

       1     5     8     3     4   100     7

[Maik Petersen]

Thanks, I'm almost there. Now I know how to make a set of self chosen numbers, but I still don't know how to pick a number out of the set of numbers and check whether it is equal to 8 for example. What I thought of is:

if 8 == numset
   disp('yes')
end

But obviously, matlab does not accept that. Also, I want to add numbers to it with the help of a loop, so every single loop I want to add a number to the already expanded set of numbers. My guess is:

expanded = [numset, n]

With n the number I want to add every single loop. But I see that the n of the previous loop will be excluded of the expanded set. For I could have given all of the numbers a different character, but the loop goes far beyond 26 iterations. I hope I've made myself clear, thanks in advance again.

[Matt J]

I still don't know how to pick a number out of the set of numbers and check whether it is equal to 8 for example

Through a combination of Indexing and Relational Operations

>> numset=[1 5 8 3];
>> numset(1)==8,

ans =

       0

>> numset([2,3,4])==8

ans =

       0     1     0

>> any(numset==8)

ans =

       1

Also, I want to add numbers to it with the help of a loop

That's usually a bad idea. It involves a lot of repeated memory allocation, but you can do it by iterative concatenation,

>> numset=[1,2,3]; for n=4:6, numset=[numset,n], end

numset =

       1     2     3     4

numset =

       1     2     3     4     5

numset =

       1     2     3     4     5     6

Answer 2

[Walter Roberson]

if ismember(8, numset)
  disp('yes')
end