sort

The C++ interface for sort. More...

array	sort (const array &in, int dim=-1, bool isdescending=false)
	Sort array along dimension. More...
void	sort (array &values, array &indices, const array &in, int dim=-1, bool isdescending=false)
	Sort array along dimension and return original indices of sorted values. More...
void	sort (array &outkeys, array &outvalues, const array &keys, const array &values, bool isdescending=false)
	Sort array values based on keys along dimension. More...

Detailed Description

The C++ interface for sort.

Sorting an array reorders the elements in the array along the dimension specified.

The defualt order is ascending order. That is, the smallest element along the dimension is places at the first index location and the largest element is placed at the last location. To sort in descending order, set the isdescending flag to true.

The indices array parameter can be used to retrieve the indices of the elements before the sort.

array a = rand(5); //a = [6]
                   //    [9]
                   //    [1]
                   //    [7]
                   //    [4]

a = sort(a,0);     //a = [1]
                   //    [4]
                   //    [6]
                   //    [7]
                   //    [9]

array a = rand(5); //a = [6]
                   //    [9]
                   //    [1]
                   //    [7]
                   //    [4]

array out,indices;
sort(out,indices,a,0);
     //out,indices = [1],[2]
     //              [4],[4]
     //              [6],[0]
     //              [7],[3]
     //              [9],[1]

The next sort function can sort the values of an array (value) based on another array (key). The function first sorts the key array and uses the indices from this sort to reorder the value array.

float keys[]   = {1, 6, 2, 5, 3, 4};

array value(6,1,values); // [5 10 41  2  5  7]
array key(6,1,keys);     // [1  6  2  5  3  4]

array outkeys,outvalues;
sort(outkeys,outvalues,key,value);

print(outvalues); // [5 41  5  7  2 10]
print(outkeys);   // [1  2  3  4  5  6]

The function sortdim uses one of the dimensions as key to sort the array.

// sort rows based on first column
array a = floor(5 * randu(5,5));
array b = sortdim(a);

array a = floor(5 * randu(5,5));
const int order[] = {3, 1};
array d = sortdim(a, 0, 2, order);

Function Documentation

array af::sort	(	const array &	in,
		int	dim = -1,
		bool	isdescending = false
	)

Sort array along dimension.

array a = rand(5); //a = [6]
                   //    [9]
                   //    [1]
                   //    [7]
                   //    [4]

a = sort(a,0);     //a = [1]
                   //    [4]
                   //    [6]
                   //    [7]
                   //    [9]

Parameters

[in]	in
[in]	dim	dimension along which to operate (-1 indicates first non-singleton dimension)
[in]	isdescending	true if descending order, false (default) in ascending order

Returns

sorted array

void af::sort	(	array &	values,
		array &	indices,
		const array &	in,
		int	dim = -1,
		bool	isdescending = false
	)

Sort array along dimension and return original indices of sorted values.

array a = rand(5); //a = [6]
                   //    [9]
                   //    [1]
                   //    [7]
                   //    [4]

array out,indices;
sort(out,indices,a,0);
     //out,indices = [1],[2]
     //              [4],[4]
     //              [6],[0]
     //              [7],[3]
     //              [9],[1]

Parameters

[out]	values
[out]	indices
[in]	in
[in]	dim	dimension along which to operate (-1 indicates first non-singleton dimension)
[in]	isdescending	true if descending order, false (default) in ascending order

void af::sort	(	array &	outkeys,
		array &	outvalues,
		const array &	keys,
		const array &	values,
		bool	isdescending = false
	)

Sort array values based on keys along dimension.

float values[] = {5,10,41, 2, 5, 7};
float keys[]   = {1, 6, 2, 5, 3, 4};

array value(6,1,values); // [5 10 41  2  5  7]
array key(6,1,keys);     // [1  6  2  5  3  4]

array outkeys,outvalues;
sort(outkeys,outvalues,key,value);

print(outvalues); // [5 41  5  7  2 10]
print(outkeys);   // [1  2  3  4  5  6]

Parameters

[out]	outkeys
[out]	outvalues
[in]	keys
[in]	values
[in]	isdescending	true if descending order, false (default) in ascending order