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.
1) In information technology, a character is a printable symbol having phonetic or pictographic meaning and usually forming part of a word of text, depicting a numeral, or expressing grammatical punctuation. new standard, Unicode, is supported by later Windows systems. 2) A distinction is sometimes made between a character and a glyph. In this distinction, a character can be distinguished from other characters in terms of meaning and sound and a glyph is the graphic image used to portray the character.