Операции над массивами

Функции dot, cross, norm и др.

Сортировка массива

Проверка упорядоченности

Issorted

Determine whether set elements are in sorted order

TF = issorted(A) returns logical 1 (true) if the elements of A are in sorted order, and logical 0 (false) otherwise. Input A can be a vector or an N-by-1 or 1-by-N cell array of strings. A is considered to be sorted if A and the output of sort(A) are equal.

TF = issorted(A, 'rows') returns logical 1 (true) if the rows of two-dimensional matrix A are in sorted order, and logical 0 (false) otherwise. Matrix A is considered to be sorted if A and the output of sortrows(A) are equal.

Note Only the issorted(A) syntax supports A as a cell array of strings.

For character arrays, issorted uses ASCII, rather than alphabetical, order.

You cannot use issorted on arrays of greater than two dimensions.

Example 1 — Using issorted on a vector

A = [5 12 33 39 78 90 95 107 128 131];

issorted(A)

ans = 1

Example 2 — Using issorted on a matrix

A = magic(5)

A =

17 24 1 8 15

23 5 7 14 16

4 6 13 20 22

10 12 19 21 3

11 18 25 2 9

issorted(A, 'rows')

ans = 0

B = sortrows(A)

B =

4 6 13 20 22

10 12 19 21 3

11 18 25 2 9

17 24 1 8 15

23 5 7 14 16

issorted(B)

ans = 1

Сортировка столбцов

Sortrows

B = sortrows(A) sorts the rows of A in ascending order. Argument A must be either a matrix or a column vector. For strings, this is the familiar dictionary sort. When A is complex, the elements are sorted by magnitude, and, where magnitudes are equal, further sorted by phase angle on the interval.

B = sortrows(A,column) sorts the matrix based on the columns specified in the vector column. If an element of column is positive, the MATLAB® software sorts the corresponding column of matrix A in ascending order; if an element of column is negative, MATLAB sorts the corresponding column in descending order. For example, sortrows(A,[2 -3]) sorts the rows of A first in ascending order for the second column, and then by descending order for the third column.

[B,index] = sortrows(A,...) also returns an index vector index.

If A is a column vector, then B = A(index). If A is an m-by-n matrix, then B = A(index,:).

Start with a mostly random matrix, A:

rand('state',0)

A = floor(rand(6,7) * 100);

A(1:4,1)=95; A(5:6,1)=76; A(2:4,2)=7; A(3,3)=73

A =

95 45 92 41 13 1 84

95 7 73 89 20 74 52

95 7 73 5 19 44 20

95 7 40 35 60 93 67

76 61 93 81 27 46 83

76 79 91 0 19 41 1

When called with only a single input argument, sortrows bases the sort on the first column of the matrix. For any rows that have equal elements in a particular column, (e.g., A(1:4,1) for this matrix), sorting is based on the column immediately to the right, (A(1:4,2) in this case):

sortrows(A)

ans =

76 61 93 81 27 46 83

76 79 91 0 19 41 1

95 7 40 35 60 93 67

95 7 73 5 19 44 20

95 7 73 89 20 74 52

95 45 92 41 13 1 84

When called with two input arguments, sortrows bases the sort entirely on the column specified in the second argument. Rows that have equal elements in this column are sorted; rows with equal elements in other columns are left in their original order:

sortrows(A,1)

ans =

76 61 93 81 27 46 83

76 79 91 0 19 41 1

95 45 92 41 13 1 84

95 7 73 89 20 74 52

95 7 73 5 19 44 20

95 7 40 35 60 93 67

This example specifies two columns to sort by: columns 1 and 7. This tells sortrows to sort by column 1 first, and then for any rows with equal values in column 1, to sort by column 7:

sortrows(A,[1 7])

ans =

76 79 91 0 19 41 1

76 61 93 81 27 46 83

95 7 73 5 19 44 20

95 7 73 89 20 74 52

95 7 40 35 60 93 67

95 45 92 41 13 1 84

Sort the matrix using the values in column 4 this time and in reverse order:

sortrows(A, -4)

ans =

95 7 73 89 20 74 52

76 61 93 81 27 46 83

95 45 92 41 13 1 84

95 7 40 35 60 93 67

95 7 73 5 19 44 20

76 79 91 0 19 41 1

Не нашли, что искали? Воспользуйтесь поиском: