Transcranial Doppler (TCD), first described in 1982 [1], is a noninvasive ultrasound (US) study that involves the use of a low-frequency (â¤2 MHz) transducer probe to insonate the basal cerebral arteries through relatively thin bone windows.
Details. as.character and is.character are generic: you can write methods to handle specific classes of objects, see InternalMethods. Further, for as.character the default method calls as.vector, so dispatch is first on methods for as.character and then for methods for as.vector.
Class methods are usually used to create instances of that class. For example, [NSString stringWithFormat:@SomeParameter]; returns an NSString instance with the parameter that is sent to it. Hence, because it is a Class method that returns an object of its type, it is also called a convenience method.