is.magic | R Documentation |

Returns `TRUE`

if the square is magic, semimagic, panmagic, associative,
normal. If argument `give.answers`

is `TRUE`

, also returns
additional information about the sums.

is.magic(m, give.answers = FALSE, func=sum, boolean=FALSE) is.panmagic(m, give.answers = FALSE, func=sum, boolean=FALSE) is.pandiagonal(m, give.answers = FALSE, func=sum, boolean=FALSE) is.semimagic(m, give.answers = FALSE, func=sum, boolean=FALSE) is.semimagic.default(m) is.associative(m) is.normal(m) is.sparse(m) is.mostperfect(m,give.answers=FALSE) is.2x2.correct(m,give.answers=FALSE) is.bree.correct(m,give.answers=FALSE) is.latin(m,give.answers=FALSE) is.antimagic(m, give.answers = FALSE, func=sum) is.totally.antimagic(m, give.answers = FALSE, func=sum) is.heterosquare(m, func=sum) is.totally.heterosquare(m, func=sum) is.sam(m) is.stam(m)

`m` |
The square to be tested |

`give.answers` |
Boolean, with |

`func` |
A function that is evaluated for each row, column, and unbroken diagonal |

`boolean` |
Boolean, with |

A semimagic square is one all of whose row sums equal all its columnwise sums (ie the magic constant).

A magic square is a semimagic square with the sum of both unbroken diagonals equal to the magic constant.

A panmagic square is a magic square all of whose broken diagonals sum to the magic constant. Ollerenshaw calls this a “pandiagonal” square.

A most-perfect square has all 2-by-2 arrays anywhere within the square summing to

*2S*where*S=n^2+1*; and all pairs of integers*n/2*distant along the same major (NW-SE) diagonal sum to*S*(note that the*S*used here differs from Ollerenshaw's because her squares are numbered starting at zero). The first condition is tested by`is.2x2.correct()`

and the second by`is.bree.correct()`

.All most-perfect squares are panmagic.

A normal square is one that contains

*n^2*consecutive integers (typically starting at 0 or 1).A sparse matrix is one whose nonzero entries are consecutive integers, starting at 1.

An associative square (also regular square) is a magic square in which

*a[i,j]+a[n+1-i,n+1-j]=n^2+1*. Note that an associative semimagic square is magic; see also`is.square.palindromic()`

. The definition extends to magic hypercubes: a hypercube`a`

is associative if`a+arev(a)`

is constant.An ultramagic square is pandiagonal and associative.

A latin square of size

*n-by-n*is one in which each column and each row comprises the integers 1 to n (not necessarily in that order). Function`is.latin()`

is a wrapper for`is.latinhypercube()`

because there is no natural way to present the extra information given when`give.answers`

is`TRUE`

in a manner consistent with the other functions documented here.An antimagic square is one whose row sums and column sums are consecutive integers; a totally antimagic square is one whose row sums, column sums, and two unbroken diagonals are consecutive integers. Observe that an antimagic square is not necessarily totally antimagic, and vice-versa.

A heterosquare has all rowsums and column sums distinct; a totally heterosquare [NB nonstandard terminology] has all rowsums, columnsums, and two long diagonals distinct.

A square is sam (or SAM) if it is sparse and antimagic; it is stam (or STAM) if it is sparse and totally antimagic. See documentation at

`SAM`

.

Returns `TRUE`

if the square is semimagic, etc. and `FALSE`

if not.

If `give.answers`

is taken as an argument and is `TRUE`

,
return a list of at least five elements. The first element of the
list is the answer: it is `TRUE`

if the square is (semimagic,
magic, panmagic) and `FALSE`

otherwise. Elements 2-5 give the
result of a call to `allsums()`

, viz: rowwise and columnwise
sums; and broken major (ie NW-SE) and minor (ie NE-SW) diagonal sums.

Function `is.bree.correct()`

also returns the sums of
elements distant *n/2* along a major diagonal
(`diag.sums`

); and function `is.2x2.correct()`

returns the
sum of each *2x2* submatrix (`tbt.sums`

); for
other size windows use `subsums()`

directly.
Function `is.mostperfect()`

returns both of these.

Function `is.semimagic.default()`

returns `TRUE`

if the
argument is semimagic [with respect to `sum()`

] using a faster
method than `is.semimagic()`

.

Functions that take a `func`

argument apply that function to each
row, column, and diagonal as necessary. If `func`

takes its
default value of `sum()`

, the sum will be returned; if
`prod()`

, the product will be returned, and so on. There are
many choices for this argument that produce interesting tests;
consider `func=max`

, for example. With this, a “magic”
square is one whose row, sum and (unbroken) diagonals have identical
maxima. Thus `diag(5)`

is magic with respect to `max()`

,
but `diag(6)`

isn't.

Argument `boolean`

is designed for use with non-default values
for the `func`

argument; for example, a latin square is semimagic
with respect to `func=function(x){all(diff(sort(x))==1)}`

.

Function `is.magic()`

is vectorized; if a list is supplied, the
defaults are assumed.

Robin K. S. Hankin

https://mathworld.wolfram.com/MagicSquare.html

`minmax`

,`is.perfect`

,`is.semimagichypercube`

,`sam`

is.magic(magic(4)) is.magic(diag(7),func=max) # TRUE is.magic(diag(8),func=max) # FALSE stopifnot(is.magic(magic(3:8))) is.panmagic(panmagic.4()) is.panmagic(panmagic.8()) data(Ollerenshaw) is.mostperfect(Ollerenshaw) proper.magic <- function(m){is.magic(m) & is.normal(m)} proper.magic(magic(20))

magic documentation built on Nov. 16, 2022, 9:06 a.m.

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