MATLAB POLYSPACE RELEASE NOTES Bedienungsanleitung PDF herunterladen (Seite 31)

Matrices and Mag ic Squares

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Subscript expressions involving colons refer to portions of a matrix:

A(1:k,j)

is the first k elements of the jth column of A.So

sum(A(1:4,4))

computes the sum of the fourth colum

n. But there is a better way. The colon

by itself refers to all the elements

in a r ow or column of a matrix and the

keyword

end refers to the last row or

column. So

sum(A(:,end))

computes the sum of the elements in the last column of A:

ans =

Why is the magic sum for a 4-by-4 square equal to 34? If the integers from 1

to 16 are sorted into four groups with equal sums, that sum must be

sum(1:16)/4

which, of course, is

ans =

The magic Function

MATLAB actually has a built-in function that creates magic squares of almost

any size. Not surprisingly, this function is named

magic:

B = magic(4)

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MATLAB POLYSPACE RELEASE NOTES Bedienungsanleitung Seite 31