Fast match() function

Package providing a fast match() replacement for cases that require repeated look-ups. It is slightly faster that R's built-in match() function on first match against a table, but extremely fast on any subsequent lookup as it keeps the hash table in memory.


NEWS for fastmatch

1.1-0 (under development) o add fmatch.hash() which will create a hash table that can be used later with fmatch(). This can be used in cases where attaching the hash to the table implicitly is not reliable.

o	added ctapply() - a fast version of tapply()

o	added coalesce() - fast way of grouping unique values into
contiguous groups (in linear time).

o	added %fin% - a fast version of %in%

o	fastmatch now supports long vectors. Note that the hash
function is the same as in R and thus it uses at most 32-bits,
hence long vectors can be used, but they must have less than
2^32 (~4e9) unique values.

o	bugfix: matching reals against a table that contains NA or NaNs
would not match the position of those but return NA instead.

o	bugfix: fix crash when a newly unserialized hash table is
used (since the table hash is not stored during serialization).

1.0-4 2012-01-12 o some R functions (such as subset assignment like x[1] <- 2) can create a new object (with possibly modified content) and copy all attributes including the hash cache. If the original object was used as a table in fmatch(), the hash cache will be copied into the modified object and thus its cache will be possibly out of sync with the object. fmatch() will now identify such cases and discard the hash to prevent errorneous results.

1.0-3 2011-12-21 o match() coerces POSIXlt objects into characters, but so far fmatch() performed the match on the actual objects. Now fmatch() coerces POSIXlt object into characters just like match(), but note that you will lose the ability to perform fast lookups if the table is a POSIXlt object -- please use POSIXct objects (much more efficient) or use as.character() on the POSIXlt object to create a table that you want to re-use.

1.0-2 2011-09-14 o bugfix: nomatch was ignored in the fastmatch implementation (thanks to Enrico Schumann for reporting)

1.0-1 2010-12-23 o minor cleanups

1.0-0 2010-12-23 o initial release

Reference manual

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1.1-0 by Simon Urbanek, a year ago

Browse source code at

Authors: Simon Urbanek <[email protected]>

Documentation:   PDF Manual  

GPL-2 license

Imported by CEGO, ITNr, Kernelheaping, RSNPset,, TeXCheckR, dexter, ffbase, grattan, heims, hutils, phangorn, quanteda.

Depended on by networkR.

Suggested by checkmate.

See at CRAN