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85 lines
2.5 KiB
Plaintext
85 lines
2.5 KiB
Plaintext
NAME
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indices - indices for specified matrix or association element
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SYNOPSIS
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indices(V, index)
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TYPES
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V matrix or association
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index integer
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return list with up to 4 elements
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DESCRIPTION
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For 0 <= index < size(V), indices(V, index) returns list(i_0, i_1, ...)
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for which V[i_0, i_1, ...] is the same lvalue as V[[index]].
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For other values of index, a null value is returned.
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This function can be useful for determining those elements for which
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the indices satisfy some condition. This is particularly so for
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associations since these have no simple relation between the
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double-bracket index and the single-bracket indices, which may be
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non-integer numbers or strings or other types of value. The
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information provided by indices() is often required after the use
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of search() or rsearch() which, when successful, return the
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double-bracket index of the item found.
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EXAMPLE
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; mat M[2,3,1:5]
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; indices(M, 11)
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list (3 elements, 2 nonzero):
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[[0]] = 0
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[[1]] = 2
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[[2]] = 2
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; A = assoc();
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; A["cat", "dog"] = "fight";
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; A[2,3,5,7] = "primes";
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; A["square", 3] = 9
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; indices(A, search(A, "primes"))
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list (4 elements, 4 nonzero):
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[[0]] = 2
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[[1]] = 3
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[[2]] = 5
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[[3]] = 7
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LIMITS
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abs(index) < 2^31
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LINK LIBRARY
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LIST* associndices(ASSOC *ap, long index)
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LIST* matindices(MATRIX *mp, long index)
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SEE ALSO
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assoc, mat
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## Copyright (C) 1999-2006 Landon Curt Noll
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##
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## Calc is open software; you can redistribute it and/or modify it under
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## the terms of the version 2.1 of the GNU Lesser General Public License
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## as published by the Free Software Foundation.
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##
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## Calc is distributed in the hope that it will be useful, but WITHOUT
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## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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## or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
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## Public License for more details.
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##
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## A copy of version 2.1 of the GNU Lesser General Public License is
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## distributed with calc under the filename COPYING-LGPL. You should have
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## received a copy with calc; if not, write to Free Software Foundation, Inc.
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## 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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##
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## @(#) $Revision: 30.1 $
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## @(#) $Id: indices,v 30.1 2007/03/16 11:10:42 chongo Exp $
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## @(#) $Source: /usr/local/src/bin/calc/help/RCS/indices,v $
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##
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## Under source code control: 1999/11/16 08:02:03
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## File existed as early as: 1999
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##
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## chongo <was here> /\oo/\ http://www.isthe.com/chongo/
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## Share and enjoy! :-) http://www.isthe.com/chongo/tech/comp/calc/
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