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59 lines
1.4 KiB
Plaintext
59 lines
1.4 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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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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