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.
Character (arts) A character (sometimes known as a fictional character) is a person or other being in a narrative work of art (such as a novel, play, television series, or film). The character may be entirely fictional or based on a real-life person, in which case the distinction of a fictional versus real character may be made.