Documentation - C API
kmeans.c File Reference

K-means - Declaration. More...

#include "kmeans.h"
#include "generic.h"
#include "mathop.h"
#include <string.h>
#include "shuffle-def.h"

Functions

void vl_kmeans_reset (VlKMeans *self)
 Reset state.
VlKMeansvl_kmeans_new (vl_type dataType, VlVectorComparisonType distance)
 Create a new KMeans object.
VlKMeansvl_kmeans_new_copy (VlKMeans const *kmeans)
 Create a new KMeans object by copy.
void vl_kmeans_delete (VlKMeans *self)
 Deletes a KMeans object.
void vl_kmeans_set_centers (VlKMeans *self, void const *centers, vl_size dimension, vl_size numCenters)
 Set centers.
void vl_kmeans_init_centers_with_rand_data (VlKMeans *self, void const *data, vl_size dimension, vl_size numData, vl_size numCenters)
 init centers by randomly sampling data
void vl_kmeans_init_centers_plus_plus (VlKMeans *self, void const *data, vl_size dimension, vl_size numData, vl_size numCenters)
 Seed centers by the KMeans++ algorithm.
void vl_kmeans_quantize (VlKMeans *self, vl_uint32 *assignments, void *distances, void const *data, vl_size numData)
 Quantize data.
void vl_kmeans_quantize_ann (VlKMeans *self, vl_uint32 *assignments, void *distances, void const *data, vl_size numData, vl_bool update)
 Quantize data using approximate nearest neighbours (ANN).
double vl_kmeans_refine_centers (VlKMeans *self, void const *data, vl_size numData)
 Refine center locations.
double vl_kmeans_cluster (VlKMeans *self, void const *data, vl_size dimension, vl_size numData, vl_size numCenters)
 Cluster data.

Detailed Description

Author:
Andrea Vedaldi, David Novotny

Function Documentation

double vl_kmeans_cluster ( VlKMeans self,
void const *  data,
vl_size  dimension,
vl_size  numData,
vl_size  numCenters 
)
Parameters:
selfKMeans object.
datadata to quantize.
dimensiondata dimension.
numDatanumber of data points.
numCentersnumber of clusters.
Returns:
K-means energy at the end of optimization.

The function initializes the centers by using the initialization algorithm set by vl_kmeans_set_initialization and refines them by the quantization algorithm set by vl_kmeans_set_algorithm. The process is repeated one or more times (see vl_kmeans_set_num_repetitions) and the resutl with smaller energy is retained.

void vl_kmeans_delete ( VlKMeans self)
Parameters:
selfKMeans object instance.

The function deletes the KMeans object instance created by vl_kmeans_new.

void vl_kmeans_init_centers_plus_plus ( VlKMeans self,
void const *  data,
vl_size  dimension,
vl_size  numData,
vl_size  numCenters 
)
Parameters:
selfKMeans object.
datadata to sample from.
dimensiondata dimension.
numDatanmber of data points.
numCentersnumber of centers.
void vl_kmeans_init_centers_with_rand_data ( VlKMeans self,
void const *  data,
vl_size  dimension,
vl_size  numData,
vl_size  numCenters 
)
Parameters:
selfKMeans object.
datadata to sample from.
dimensiondata dimension.
numDatanmber of data points.
numCentersnumber of centers.

The function inits the KMeans centers by randomly sampling the data data.

VlKMeans* vl_kmeans_new ( vl_type  dataType,
VlVectorComparisonType  distance 
)
Parameters:
dataTypetype of data (VL_TYPE_FLOAT or VL_TYPE_DOUBLE)
distancedistance.
Returns:
new KMeans object instance.
VlKMeans* vl_kmeans_new_copy ( VlKMeans const *  kmeans)
Parameters:
kmeansKMeans object to copy.
Returns:
new copy.
void vl_kmeans_quantize ( VlKMeans self,
vl_uint32 assignments,
void *  distances,
void const *  data,
vl_size  numData 
)
Parameters:
selfKMeans object.
assignmentsdata to closest center assignments (output).
distancesdata to closest center distance (output).
datadata to quantize.
numDatanumber of data points to quantize.
void vl_kmeans_quantize_ann ( VlKMeans self,
vl_uint32 assignments,
void *  distances,
void const *  data,
vl_size  numData,
vl_bool  update 
)
Parameters:
selfKMeans object.
assignmentsdata to centers assignments (output).
distancesdata to closes center distance (output)
datadata to quantize.
numDatanumber of data points.
updatechoose wether to update current assignments.

The function uses an ANN procedure to compute the approximate nearest neighbours of the input data point.

Setting update to VL_TRUE will cause the algorithm to update existing assignments. This means that each element of assignments and distances is updated ony if the ANN procedure can find a better assignment of the existing one.

double vl_kmeans_refine_centers ( VlKMeans self,
void const *  data,
vl_size  numData 
)
Parameters:
selfKMeans object.
datadata to quantize.
numDatanumber of data points.
Returns:
K-means energy at the end of optimization.

The function calls the underlying K-means quantization algorithm (VlKMeansAlgorithm) to quantize the specified data data. The function assumes that the cluster centers have already been assigned by using one of the seeding functions, or by setting them.

void vl_kmeans_reset ( VlKMeans self)

The function reset the state of the KMeans object. It deletes any stored centers, releasing the corresponding memory. This cancels the effect of seeding or setting the centers, but does not change the other configuration parameters.

void vl_kmeans_set_centers ( VlKMeans self,
void const *  centers,
vl_size  dimension,
vl_size  numCenters 
)
Parameters:
selfKMeans object.
centerscenters to copy.
dimensiondata dimension.
numCentersnumber of centers.