countByKey

Counts the non-zero values of an input array according to an array of keys. More...

Functions
AFAPI void	countByKey (array &keys_out, array &vals_out, const array &keys, const array &vals, const int dim=-1)
	C++ Interface for counting non-zero values in an array according to a key.
AFAPI af_err	af_count_by_key (af_array *keys_out, af_array *vals_out, const af_array keys, const af_array vals, const int dim)
	C Interface for counting non-zero values in an array according to key.

Detailed Description

Counts the non-zero values of an input array according to an array of keys.

All non-zero values corresponding to each group of consecutive equal keys will be counted. Keys can repeat, however only consecutive key values will be considered for each reduction. If a key value is repeated somewhere else in the keys array it will be considered the start of a new reduction. There are two outputs: the reduced set of consecutive keys and the corresponding final reduced values. An example demonstrating the reduction behavior can be seen in the following snippet.

 
    array keys(9, hkeys);  // keys = [ 0 0 1 1 1 0 0 2 2 ]
    array vals(9, hvals);  // vals = [ 1 1 0 1 1 0 0 1 0 ];
 
    array okeys, ovals;
    countByKey(okeys, ovals, keys, vals);
 
    // okeys = [ 0 1 0 2 ]
    // ovals = [ 2 2 0 1 ]
 

The keys input type must be an integer type(s32 or u32). The values return type will be of type u32.

The input keys must be a 1-D vector matching the size of the reduced dimension. In the case of multiple dimensions in the input values array, the dim parameter specifies which dimension to reduce along. An example of multi-dimensional reduce by key can be seen below:

 
    array keys(5, hkeys);
    array vals(2, 5, hvals);
 
    // keys = [ 1 0 0 2 2 ]
 
    // vals = [[ 1 1 1 0 1 ]
    //         [ 0 1 0 1 1 ]]
 
    const int reduce_dim = 1;
    array okeys, ovals;
    countByKey(okeys, ovals, keys, vals, reduce_dim);
 
    // okeys = [ 1 0 2 ]
 
    // ovals = [[ 1 2 1 ],
    //          [ 0 1 2 ]]
 

Function Documentation

af_count_by_key()

AFAPI af_err af_count_by_key	(	af_array *	keys_out,
		af_array *	vals_out,
		const af_array	keys,
		const af_array	vals,
		const int	dim
	)

C Interface for counting non-zero values in an array according to key.

Parameters

[out]	keys_out	will contain the reduced keys in vals along dim
[out]	vals_out	will contain the count of all values in vals along dim according to keys
[in]	keys	is the key array
[in]	vals	is the array containing the values to be reduced
[in]	dim	The dimension along which the non-zero values are counted

Returns

AF_SUCCESS if the execution completes properly

countByKey()

AFAPI void countByKey	(	array &	keys_out,
		array &	vals_out,
		const array &	keys,
		const array &	vals,
		const int	dim = -1
	)

C++ Interface for counting non-zero values in an array according to a key.

Parameters

[out]	keys_out	will contain the reduced keys in vals along dim
[out]	vals_out	will contain the count of all values in vals along dim according to keys
[in]	keys	is the key array
[in]	vals	is the array containing the values to be reduced
[in]	dim	The dimension along which the count operation occurs

Note

dim is -1 by default. -1 denotes the first non-singleton dimension.

NaN values are treated as non zero.