cpos {polmineR}

Get corpus positions for a query or queries.

Description

Get matches for a query in a CQP corpus (subcorpus, partition etc.), optionally using the CQP syntax of the Corpus Workbench (CWB).

Usage

cpos(.Object, ...)

## S4 method for signature 'corpus'
cpos(
  .Object,
  query,
  p_attribute = getOption("polmineR.p_attribute"),
  cqp = is.cqp,
  regex = FALSE,
  check = TRUE,
  verbose = TRUE,
  ...
)

## S4 method for signature 'character'
cpos(
  .Object,
  query,
  p_attribute = getOption("polmineR.p_attribute"),
  cqp = is.cqp,
  check = TRUE,
  verbose = TRUE,
  ...
)

## S4 method for signature 'slice'
cpos(
  .Object,
  query,
  cqp = is.cqp,
  check = TRUE,
  p_attribute = getOption("polmineR.p_attribute"),
  verbose = TRUE,
  ...
)

## S4 method for signature 'partition'
cpos(
  .Object,
  query,
  cqp = is.cqp,
  check = TRUE,
  p_attribute = getOption("polmineR.p_attribute"),
  verbose = TRUE,
  ...
)

## S4 method for signature 'subcorpus'
cpos(
  .Object,
  query,
  cqp = is.cqp,
  check = TRUE,
  p_attribute = getOption("polmineR.p_attribute"),
  verbose = TRUE,
  ...
)

## S4 method for signature 'matrix'
cpos(.Object)

## S4 method for signature 'hits'
cpos(.Object)

## S4 method for signature ''NULL''
cpos(.Object)

Arguments

.Object

A length-one character vector indicating a CWB corpus, or a corpus, or partition object.

...

Used for reasons of backwards compatibility to process arguments that have been renamed (e.g. pAttribute).

query

A character vector providing one or multiple queries (token to look up, regular expression or CQP query). Token ids (i.e. integer values) are also accepted. If query is neither a regular expression nor a CQP query, a sanity check removes accidental leading/trailing whitespace, issuing a respective warning.

p_attribute

The p-attribute to search. Needs to be stated only if query is not a CQP query. Defaults to NULL.

cqp

Either logical (TRUE if query is a CQP query), or a function to check whether query is a CQP query or not (defaults to is.cqp auxiliary function).

regex

Interpret query as a regular expression.

check

A logical value, whether to check validity of CQP query using check_cqp_query.

verbose

A logical value, whether to show messages.

Details

The cpos()-method returns a two-column matrix with the ranges (start end end corpus positions of the matches) matched by a query. CQP syntax can be used. The encoding of the query is adjusted to conform to the encoding of the CWB corpus. If there are not matches, NULL is returned.

Previous polmineR versions defined the cpos()-method for matrix and hits objects to obtain an integer vector with unfolded individual corpus positions. This usage is deprecated starting with polmineR v0.8.8

Value

A matrix with two columns. The first column reports the left/starting corpus positions (cpos) of the hits obtained. The second column reports the right/ending corpus positions of the respective hit. The number of rows is the number of hits. If there are no hits, NULL is returned.

Examples

use(pkg = "RcppCWB", corpus = "REUTERS")

# look up single tokens
cpos("REUTERS", query = "oil")
corpus("REUTERS") %>% cpos(query = "oil")

corpus("REUTERS") %>%
  subset(grepl("saudi-arabia", places)) %>%
  cpos(query = "oil")
  
partition("REUTERS", places = "saudi-arabia", regex = TRUE) %>%
  cpos(query = "oil")

# use CQP query syntax
cpos("REUTERS", query = '"Saudi" "Arabia"')
corpus("REUTERS") %>% cpos(query = '"Saudi" "Arabia"')
corpus("REUTERS") %>%
  subset(grepl("saudi-arabia", places)) %>%
  cpos(query = '"Saudi" "Arabia"', cqp = TRUE)
partition("REUTERS", places = "saudi-arabia", regex = TRUE) %>%
  cpos(query = '"Saudi" "Arabia"', cqp = TRUE)