1. A computer-implemented method for analyzing a physiological signal, comprising: selecting a first time interval containing a pattern of interest in a recording of the physiological signal; computing respective values of a characteristic of the physiological signal using respective characters in a plurality of time segments within the first time interval such that each segment is represented by a character, wherein each character represents an increase in the physiological signal or a decrease in the physiological signal for each segment in the plurality of time segments; concatenating the computed values to form a signature of the pattern of interest by augmenting the characters to form a string; and identifying a further occurrence of the pattern of interest in the physiological signal during a second time interval by matching the signal in the second time interval to the signature.