Examples
These examples demonstrate pattern matching in the MatchRegex operator.
Example 1: Simple concatenation
The predicates that are used in the example are:
param
predicates: {
big=i>1000,
middle=i>10 && i<1000,
little=i<10 };
If you use a pattern of big little, a sequence of tuples where i has the values of:
- 2000, 0 is a match.
- 2000, 100, 10 is not a match, because the value 100 does not fit the pattern.
Example 2: A simple example of disjunction and grouping.
If you use the same predicates as the previous example, and a pattern of (big | middle) little:
- 2000, 10 is a match.
- 100, 10 is a match.
Example 3: A simple example of optional expressions.
If you use the same predicates as the previous examples, and a pattern of big middle? little:
- 2000, 10 is a match.
- 2000, 100, 10 is a match.
Example 4: Detecting patterns in stock prices.
In the following example, the input stream Quotes consists of stock price information over time. The task is to detect "M-shape" patterns, also known as double-peak formation. In other words, the pattern detects two rise and drop peaks, followed by a deep drop below the start of the pattern.
stream<MatchT> Matches = MatchRegex(Quotes) {
param
pattern : ". rise+ drop+ rise+ drop* deep";
partitionBy : symbol;
predicates : {
rise = price>First(price) && price>=Last(price),
drop = price>=First(price) && price<Last(price),
deep = price<First(price) && price<Last(price)
};
output
Matches : symbol=symbol, seqNum=First(seqNum),
count=Count(), maxPrice=Max(price);
}