Re: Matlab test for magic requested

[Nicholas Jankowski]

On Sun, Dec 13, 2015 at 7:18 PM, Richard Balogh <address@hidden> wrote:

On 12.12.2015 22:12, Andreas Weber wrote:

Hi Richard, thank you very much.

Am 12.12.2015 um 19:50 schrieb Richard Balogh:

magic (1.5)

ans =

      1

Oh, this wasn't expected. Can you try other non integer values? For
example magic(2.1), magic(2.8), can you see a system?

 magic(2.1)

ans =

     1     3
     4     2

>>  magic(2.8)

ans =

     1     3
     4     2

From the magic help:


"If you supply n less than 3, magic returns either a nonmagic square, or else the degenerate magic squares 1 and []."

if you step through 0 to 3, the ruleset basically follows:

magic(n), 0<=n<1 = []    (tested to 1-eps)

magic(n), 1<=n<2 = 1   (tested to 2-eps)

magic(n), 2<=n<3 = [1,3;4,2]  (tested to 3-eps)

also, note results from negatives:

magic(0) = []

magic(-0.1) = []

magic(-1) = []

magic (-2)
Subscript indices must either be real positive integers or logicals.

Error in magic (line 35)
   M([i; i+p],j) = M([i+p; i],j);

magic(-1+eps) = []

magic(-1-eps)
Subscript indices must either be real positive integers or logicals.

Error in magic (line 35)
   M([i; i+p],j) = M([i+p; i],j);

nick j.