Since ‘A’ appears more than 1/3 times in the first element of the input stream, it appears in the first element of the output stream. For example, ‘B’ appears in keys in the 3rd element of the output stream but ‘B’ does not appear more than 3/3 times in the first 3 elements of the input stream. (Note that keys in the N-th element of the output stream may contain items that do not appear more than N/ k times in the first N elements of the input stream.
The output stream could contain only keys because keys contains the candidates for the most frequent items however, counts is provided to see how the algorithm operates.įor example, if the input stream is, and k = 3, so that the N-th value of keys contains all items in the input stream that appear more than N/3 times, then the output stream is: The elements of the output stream are pairs ( keys, counts) where keys is a list of k -1 items from the input stream or a special symbol None, and counts is a list of k -1 nonnegative integers where the number of times keys appears in the first N elements of the input stream is at most counts.
The agent has a parameter, k, where if any item occurs more than N/ k times in the first N items of the input stream then that item will appear in the N-th element of the output stream. Given an input stream of arbitrary items, this agent outputs a stream of candidates for the most frequent items in the input stream. Misra-Gries Algorithm: Identifying frequent items Count Min Sketch, Bloom Filters and Heavy Hitters operations on streams are direct implementations of the map_element and map_window agents to classes from PyProbables, which is an open-source rich collection of programs operating on probabilistic data structures.
#Multi counter on stream how to
This section shows how to use IoTPy to wrap code for terminating functions to count items in streams.
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