convenience.go
func (r *Registry) Derive(name string, tags []string, v float64) *Derive {
	factory := func() interface{} { return NewDerive(v) }
	return r.fetchDerive(name, tags, factory)
}
func (r *Registry) Derive(name string, tags []string, v float64) *Derive {
	factory := func() interface{} { return NewDerive(v) }
	return r.fetchDerive(name, tags, factory)
}
func ( r * Registry ) Derive ( name string , tags [ ] string , v float64 ) * Derive { factory := func ( ) interface { } { return NewDerive ( v ) } return r . fetchDerive ( name , tags , factory ) }
// Derive fetches an instrument from the registry or creates a new one.
//
// If another instrument type is already registered with the same
// name/tags, a blank one will be returned and an error
// will be logged to the Errors() channel.
Derive fetches an instrument from the registry or creates a new one . If another instrument type is already registered with the same name / tags a blank one will be returned and an error will be logged to the Errors () channel .