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Classes | Functions | Variables

Subscripted array indexing

Basics

Get or set part of an array. More...

Classes

class  seq

Functions

array row (int i) const
 Access row i to form row vector.
array col (int i) const
 Access column i to form column vector.
array slice (int i) const
 Access slice i to form a matrix.
array rows (int first, int last) const
 Access rows first through last to form a matrix.
array cols (int first, int last) const
 Access columns first through last to form a matrix.
array slices (int first, int last) const
 Access slices first through last to form a volume.
template<typename ty >
array & operator= (const ty)
 scalar assignment
array & operator= (const array &)
 array assignment

Variables

int end
 Reference last element in dimension.
seq span
 Reference entire dimension.

One subscript

array operator() (int x) const
 Access linear element x.
array operator() (const seq &) const
 Access linear sequence of elements.
array operator() (array indices) const
 Use indices (integer values or boolean mask)

Two subscripts

array operator() (const seq &, const seq &) const
 Access submatrix.
array operator() (int row, int col) const
 Access linear element at row and col.
array operator() (int row, const seq &y) const
 Access linear sequence of elements along row.
array operator() (int row, array columns) const
 Elements along row and columns.
array operator() (const seq &x, int column) const
 Access linear sequence of elements along column.
array operator() (const seq &rows, array columns) const
 Elements along rows and columns.
array operator() (array rows, int column) const
 Elements along rows and column.
array operator() (array rows, const seq &columns) const
 Elements along rows and columns.
array operator() (array rows, array columns) const
 Elements along rows and columns.

Three subscripts

array operator() (const seq &, const seq &, const seq &) const
 Access volume.
array operator() (int x, int y, int z) const
 Access element.
array operator() (const seq &x, int y, int z) const
 Access vector.
array operator() (int x, const seq &y, int z) const
 Access vector.
array operator() (int x, int y, const seq &z) const
 Access vector.
array operator() (int x, const seq &y, const seq &z) const
 Access matrix.
array operator() (const seq &x, const seq &y, int z) const
 Access matrix.
array operator() (const seq &x, int y, const seq &z) const
 Access matrix.
array operator() (array rows, array cols, const seq &slices) const
 Elements along rows, columns, slices.
array operator() (array rows, array cols, int slice) const
 Elements along rows, cols, slice.
array operator() (array rows, const seq &cols, const seq &slices) const
 Elements along rows, columns, slices.
array operator() (array rows, const seq &cols, int slice) const
 Elements along rows, cols, slice.
array operator() (const seq &rows, array cols, const seq &slices) const
 Elements along rows, columns, slices.
array operator() (const seq &, const seq &, array) const
 Access submatrix.

Four subscripts

array operator() (const seq &w, const seq &x, const seq &y, const seq &z) const
 Access volume.
array operator() (const seq &w, const seq &x, const seq &y, int z) const
 Access volume.
array operator() (const seq &w, const seq &x, int y, int z) const
 Access matrix.

Detailed Description

Get or set part of an array.

For more examples, see Indexing.

    array a = randu(3,4);
    print(a);
    print(a.col(0));
    print(a(4));
    print(a(seq(3)));
    a.col(end) = -1;  // set last column
    print(a);
    print(a(a > .5));

produces: 

a =
        0.7402      0.9690      0.6673      0.5132
        0.9210      0.9251      0.1099      0.7762
        0.0390      0.4464      0.4702      0.2948

a.col(0) =
        0.7402
        0.9210
        0.0390

a(4) =
        0.9251

a(seq(3)) =
        0.7402
        0.9210
        0.0390

a =
        0.7402      0.9690      0.6673     -1.0000
        0.9210      0.9251      0.1099     -1.0000
        0.0390      0.4464      0.4702     -1.0000

a(a > .5) =
        0.7402
        0.9210
        0.9690
        0.9251
        0.6673

Use seq objects to create numeric sequences for subscripting or arithmetic. See also Indexing.

    array A = randu(5,1);
    array B = A(seq(0,3)); // extract elements {0,1,2,3}

Sequences can also be combined with arithmetic after casting: 

    randu(1,5) + array(seq(3, 3, 16));
See also:
Indexing

For examples, see Indexing.

Function Documentation

array row ( int  i) const [inline, inherited]

Access row i to form row vector.

Examples:
examples/misc/hello_world.cpp, and examples/misc/integer.cpp.
array col ( int  i) const [inline, inherited]

Access column i to form column vector.

Examples:
examples/image/image_demo.cpp, examples/misc/hello_world.cpp, and examples/misc/integer.cpp.
array slice ( int  i) const [inline, inherited]

Access slice i to form a matrix.

array rows ( int  first,
int  last 
) const [inline, inherited]

Access rows first through last to form a matrix.

array cols ( int  first,
int  last 
) const [inline, inherited]

Access columns first through last to form a matrix.

array slices ( int  first,
int  last 
) const [inline, inherited]

Access slices first through last to form a volume.

array operator() ( int  x) const [inline, inherited]

Access linear element x.

array operator() ( const seq &  ) const [inherited]

Access linear sequence of elements.

array operator() ( array  indices) const [inherited]

Use indices (integer values or boolean mask)

array operator() ( const seq &  ,
const seq &   
) const [inherited]

Access submatrix.

array operator() ( int  row,
int  col 
) const [inline, inherited]

Access linear element at row and col.

array operator() ( int  row,
const seq &  y 
) const [inline, inherited]

Access linear sequence of elements along row.

array operator() ( int  row,
array  columns 
) const [inline, inherited]

Elements along row and columns.

array operator() ( const seq &  x,
int  column 
) const [inline, inherited]

Access linear sequence of elements along column.

array operator() ( const seq &  rows,
array  columns 
) const [inherited]

Elements along rows and columns.

array operator() ( array  rows,
int  column 
) const [inline, inherited]

Elements along rows and column.

array operator() ( array  rows,
const seq &  columns 
) const [inherited]

Elements along rows and columns.

array operator() ( array  rows,
array  columns 
) const [inherited]

Elements along rows and columns.

array operator() ( const seq &  ,
const seq &  ,
const seq &   
) const [inherited]

Access volume.

array operator() ( int  x,
int  y,
int  z 
) const [inline, inherited]

Access element.

array operator() ( const seq &  x,
int  y,
int  z 
) const [inline, inherited]

Access vector.

array operator() ( int  x,
const seq &  y,
int  z 
) const [inline, inherited]

Access vector.

array operator() ( int  x,
int  y,
const seq &  z 
) const [inline, inherited]

Access vector.

array operator() ( int  x,
const seq &  y,
const seq &  z 
) const [inline, inherited]

Access matrix.

array operator() ( const seq &  x,
const seq &  y,
int  z 
) const [inline, inherited]

Access matrix.

array operator() ( const seq &  x,
int  y,
const seq &  z 
) const [inline, inherited]

Access matrix.

array operator() ( array  rows,
array  cols,
const seq &  slices 
) const [inherited]

Elements along rows, columns, slices.

array operator() ( array  rows,
array  cols,
int  slice 
) const [inline, inherited]

Elements along rows, cols, slice.

array operator() ( array  rows,
const seq &  cols,
const seq &  slices 
) const [inherited]

Elements along rows, columns, slices.

array operator() ( array  rows,
const seq &  cols,
int  slice 
) const [inline, inherited]

Elements along rows, cols, slice.

array operator() ( const seq &  rows,
array  cols,
const seq &  slices 
) const [inherited]

Elements along rows, columns, slices.

array operator() ( const seq &  ,
const seq &  ,
array   
) const [inherited]

Access submatrix.

array operator() ( const seq &  w,
const seq &  x,
const seq &  y,
const seq &  z 
) const [inherited]

Access volume.

array operator() ( const seq &  w,
const seq &  x,
const seq &  y,
int  z 
) const [inline, inherited]

Access volume.

array operator() ( const seq &  w,
const seq &  x,
int  y,
int  z 
) const [inline, inherited]

Access matrix.

array& operator= ( const ty  ) [inherited]

scalar assignment

array& operator= ( const array &  ) [inherited]

array assignment

Variable Documentation

int end

Reference last element in dimension. 

    float hA[] = { 0,1,2,3,4,5 };
    array A(hA,2,3);
    A(end,0) // last element in first column: 1
    A(end)   // last element of entire array: 5
    A(-1)    // equivalent to A(end)
    A(-2)    // equivalent to A(end-1)
See also:
Indexing
Examples:
examples/fdtd/fdtd.cpp, and examples/misc/hello_world.cpp.
seq span

Reference entire dimension. 

    float hA[] = { 0,1,2,3,4,5 };
    array A(hA,2,3);
    A(span,1) // reference second column: {2 3}
    A(span)   // entire array flattened as column vector
See also:
Indexing
Examples:
examples/fdtd/fdtd.cpp, examples/image/gfor_hist_demo.cpp, examples/misc/gfor.cpp, examples/misc/hello_world.cpp, and examples/misc/integer.cpp.
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