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 recognition. There are two basic types of core OCR algorithm, which may produce a ranked list of candidate characters. Matrix matching involves comparing an image to a stored glyph on a pixel-by-pixel basis; it is also known as pattern matching, pattern recognition, or image correlation.