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.
A character literal is composed of a constant character. It is represented by the character surrounded by single quotation marks. There are two kinds of character literals: Narrow-character literals of type char, for example 'a'. Wide-character literals of type wchar_t, for example L'a'.