members

Arguments

N

Needles: matrix or hypermatrix of booleans, integer-encoded numbers, real or complex decimal numbers, polynomials or texts. In "rows" or "cols" mode, no hypermatrix is accepted. A given value (or row or column) may appear several times in N.

H

Haystack: matrix or hypermatrix of same data type as N. In "rows" or "cols" mode, no hypermatrix is accepted, and N and H must have respectively the same number of columns or rows.

Options:

From one to three options may be specified in any order:

"last"

when the location in H of needles from N is querried through loc, by default the position of the first respective occurrences in H are returned. If "last" is specified, the position of the last occurrences in H are returned instead.

"rows", "cols"

By default, each element N(i, j, ...) of N is considered as a needle to search in H. If "rows" is specified, each row of N is considered as a needle -- as a whole --, and is searched among rows of H. The same applies between columns of N and H if "cols" is used.

"shuffle"

In "rows" or "cols" mode, by default the order of components of a row/column is considered: for instance, [ 7 3 5 ] in N does not match [3 5 7] in H. When "shuffle" is specified, any permutation of --say--[3 5 7] will be considered as matching a [3 5 7] row of N. This option is ignored for polynomials.

nb

In normal mode: nb(i, j, ...) returns (as reals) the number of occurrences in H of N(i, j, ...). nb and N have the same format. If H is empty, a matrix of zeros is returned. If N is empty, the empty matrix [] is returned.

In "rows" or "cols" mode: nb is a row of reals with as many components as N has rows/columns. nb(i) returns the number of occurrences in H(., :) of N(i, :) (or of N(:, i) in H(:, .) ).

loc

In normal mode: loc and N have the same format. loc(i, j, ...) returns the smallest linearized index in H where N(i, j, ...) occurs. If the "last" flag is used, the greatest linearized index is returned instead. If N(i, j, ...) in not found in H, loc(i, j, ...) is set to 0.

In "rows" or "cols" mode: loc is a row of reals with as many components as N has respectively rows or columns. loc(i) returns the index of the first line H(loc(i), :) matching N(i, :) (or the index of the first column H(:, loc(i)) matching N(:, i)). If the "shuffle" flag is additionaly specified, the order of components along the rows/columns is not considered.

Description

nb = members(N, H [,"rows"|"cols"]) returns the number of occurrences of each component or row or column of N found in H. If no match is found for an element, 0 is returned for it. The index in H of the first (default) or "last" occurrence of N(i,j,...) can be querried through a second optional output loc. If matching "rows" or "cols" are searched for, matches can ignore the order of their elements, by using the option "shuffle".

%inf and -%inf values are supported in N as well as in H. In normal mode, %nan are supported in N but not in H. In "rows" or "cols" modes, %nan are supported everywhere.

In normal element-wise mode, members(..) uses dsearch(..) to fastly proceed with booleans, integer-encoded numbers (any length 8-16-32 bits signed or not), and real numbers. For complex numbers, texts, and polynomials, a slower and more memory-consuming algorithm is used. For better performances with these types of data, for big N or/and H, the user may priorly increase the stacksize(..). For long calculations, a progression bar is displayed.

Examples

N = [1 8 4 5 2 1];
H = [9 7 4 2 1 4];

[nb, loc] = members(N, H, "last")
// Returns nb  = [1 0 2 0 1 1]: for instance, 4 appears twice in H.
// And     loc = [5 0 6 0 4 5]: the last occurrence of 4 is in sixth position in H

[nb, loc] = members(N, H)
// Returns loc = [5 0 3 0 4 5]: the 1st occurrence of 4 is in third position in H

// With hypermatrices. From previous N and H:
N = matrix(N, [3 1 2]);
H = matrix(H, [3 1 2]);
[nb, loc] = members(N, H, "last")

// With integers:
N = int8(grand(3, 2, "uin", -5, 5));
H = int8(grand(4, 4, "uin", -5, 5));
[nb, loc] = members(N, H)

// With polynomials (complex coefficients are accepted):
z = %z;
N = [z (1-z)^2 ; -4 %i*z ];
H = [2  %i*z -z  3-z  z  z^3 z];
[nb, loc] = members(N, H)

// With text:
N = [ "Hi" "Hu" "Allo"];
H = [ "Hello" "Bonjour" "Allo"
      "Holà"  "Allo"  "Hallo"
      "Hi"    "Hé"    "Salud" ];
[nb, loc] = members(N, H, "last")

// By rows:
 H = [
  3  3  0
  4  1  0
  2  0  3
  0  1  4
  3  4  3
  0  4  1
  3  1  0
  ];
 N = [
  1  2  3
  0  1  4
  3  0  3
  4  1  0
  2  0  2
  ];
 N, H
 [nb, loc] = members(N, H, "rows")
 [nb, loc] = members(N, H, "rows","last")
 [nb, loc] = members(N, H, "rows","shuffle") // [4 1 0], [0 1 4] and [0 4 1] are considered the same

// By columns: From N and H defined above:
 N = N.', H = H.'
 [nb, loc] = members(N, H, "cols", "shuffle")

See Also

• dsearch — distribute, locate and count elements of a matrix or hypermatrix in given categories
• intersect — returns the vector of common values of two vectors
• find — find indices of boolean vector or matrix true elements
• vectorfind — finds in a matrix rows or columns matching a vector

History