Fast Searching for Multiple Keywords in Multiple Texts
c(person("Matt", "Chambers", email="matt.chambers42@gmail.com", role=c("aut", "cre")),
person("Tomas", "Petricek", role=c("aut", "cph")),
person("Vanderbilt University", role="cph"))
Aho-Corasick is an optimal algorithm for finding many
keywords in a text. It can locate all matches in a text in O(N+M) time; i.e.,
the time needed scales linearly with the number of keywords (N) and the size of
the text (M). Compare this to the naive approach which takes O(N*M) time to loop
through each pattern and scan for it in the text. This implementation builds the
trie (the generic name of the data structure) and runs the search in a single
function call. If you want to search multiple texts with the same trie, the
function will take a list or vector of texts and return a list of matches to
each text. By default, all 128 ASCII characters are allowed in both the keywords
and the text. A more efficient trie is possible if the alphabet size can be
reduced. For example, DNA sequences use at most 19 distinct characters and
usually only 4; protein sequences use at most 26 distinct characters and usually
only 20. UTF-8 (Unicode) matching is not currently supported.
Matt Chambers [aut, cre],
Tomas Petricek [aut, cph],
Vanderbilt University [cph]

c(
person("Jonathan", "Callahan", email="jonathan.s.callahan@gmail.com", role=c("aut","cre")),
person("Spencer", "Pease", email="spencerpease618@gmail.com", role=c("ctb")),
person("Hans", "Martin", email="hansmrtn@gmail.com", role=c("ctb")),
person("Rex", "Thompson", email="rexs.thompson@gmail.com", role=c("ctb"))
)
Utilities for working with hourly air quality monitoring data
with a focus on small particulates (PM2.5). A compact data model is
structured as a list with two dataframes. A 'meta' dataframe contains
spatial and measuring device metadata associated with deployments at known
locations. A 'data' dataframe contains a 'datetime' column followed by
columns of measurements associated with each "device-deployment".
Algorithms to calculate NowCast and the associated Air Quality Index (AQI)
are defined at the US Environmental Projection Agency AirNow program:
<https://www.airnow.gov/sites/default/files/2020-05/aqi-technical-assistance-document-sept2018.pdf>.
dplyr, dygraphs, leaflet, lubridate, magrittr, MazamaCoreUtils
(>= 0.4.10), MazamaTimeSeries (>= 0.2.1), readr, rlang (>=
0.1.2), stringr, tidyselect, xts
knitr, markdown, testthat (>= 2.1.0), rmarkdown, roxygen2
Jonathan Callahan [aut, cre],
Spencer Pease [ctb],
Hans Martin [ctb],
Rex Thompson [ctb]