Class: Libsvm::SvmParameter

Inherits:

Object

• Object
• Libsvm::SvmParameter

Defined in:

ext/rb-libsvm/libsvm.c

Instance Method Summary

• #label_weights ⇒ Object
• #label_weights=(weight_hash) ⇒ Object

  Label weight.

Instance Method Details

#label_weights ⇒ Object

# File 'ext/rb-libsvm/libsvm.c', line 301

static VALUE cSvmParameter_label_weights(VALUE obj) {
  struct svm_parameter *param; 
  int i;
  VALUE hash,key,val;

  Data_Get_Struct(obj,struct svm_parameter,param);
  
  hash = rb_hash_new();

  for(i = 0; i < param->nr_weight; ++i) {
    key = INT2NUM(param->weight_label[i]);
    val = rb_float_new(param->weight[i]);
    rb_hash_aset(hash,key,val);
  }

  return hash;
}

#label_weights=(weight_hash) ⇒ Object

Label weight.

nr_weight, weight_label, and weight are used to change the penalty
for some classes (If the weight for a class is not changed, it is
set to 1). This is useful for training classifier using unbalanced
input data or with asymmetric misclassification cost.

nr_weight is the number of elements in the array weight_label and
weight. Each weight[i] corresponds to weight_label[i], meaning that
the penalty of class weight_label[i] is scaled by a factor of weight[i].

If you do not want to change penalty for any of the classes,
just set nr_weight to 0.

# File 'ext/rb-libsvm/libsvm.c', line 271

static VALUE cSvmParameter_label_weights_set(VALUE obj,VALUE weight_hash) {
  struct svm_parameter *param;
  int i,len,weight_label;
  double weight;
  VALUE keys,key,val;

  Data_Get_Struct(obj,struct svm_parameter,param);

  if(param->nr_weight > 0) {
    free(param->weight);
    free(param->weight_label);
  }

  param->nr_weight = rx_hash_size(weight_hash);
  param->weight = (double *)calloc(param->nr_weight,sizeof(double));
  param->weight_label = (int *)calloc(param->nr_weight,sizeof(int));

  keys = rb_funcall(weight_hash, rb_intern("keys"),0);

  for(i = 0; i < param->nr_weight; ++i) {
    key = rb_ary_entry(keys,i);
    val = rb_hash_aref(weight_hash,key);
    
    param->weight_label[i] = NUM2INT(key);
    param->weight[i] = NUM2DBL(val);
  }

  return Qnil;
}