ohsome 0.2.2

• On attach, the package now issues an informative startup message instead of a
  warning if it could not retrieve metadata information from the ohsome API.
• Vignette code chunks do not evaluate on CRAN to avoid errors when internet
  resources are temporally unavailable
• Fixed tests to use suggested packages conditionally

v0.2.1

ohsome 0.2.1

• Package CITATION file calls bibentry() instead of old-style citEntry().
• Fixed incomplete file URIs in docs.
• Fixed missing strict = FALSE in query example in README.

ohsome 0.2.0

• Added a NEWS.md file to track changes to the package.
• Added strictargument to ohsome_post. When set to TRUE (default), an error
  is thrown on invalid queries and the request is not sent to the API. Queries
  with undefined filter or time parameters are considered as invalid in strict
  mode.
• Changed behavior of set_properties(): Removes properties parameter from
  query body by default, accepts tags and/or metadata and/or
  contributionTypes as properties argument (multiple values provided as
  comma-separated character or character vector).
• Changed behavior of set_time(), set_filter(), set_groupByKeys(),
  set_groupByKey() and set_groupByValues: Return unmodified query object if
  parameter argument is missing (e.g. set_filter(query)), but remove parameter
  from body if explicitly set to NULL (e.g. set_filter(query, filter = NULL))
• Added grouping argument to ohsome_query() and set_grouping()function.
  Based on grouping, the endpoint URL is appended so that aggregations are
  grouped accordingly.
• Added return_value argument to ohsome_aggregate_elements(). Based on
  return_value, the endpoint URL is appended so that either absolute aggregate
  values, densities or ratios are requested from the ohsome API.
• Added ohsome_query() wrapper functions ohsome_extract_elements(),
  ohsome_elements_bbox, ohsome_elements_centroid and ohsome_elements_geometry
  for elements extraction endpoints of ohsome API
• Added ohsome_query() wrapper functions ohsome_extract_elementsFullHistory(),
  ohsome_elementsFullHistory_bbox(), ohsome_elementsFullHistory_centroid() and
  ohsome_elementsFullHistory_geometry() for elementsFullHistory extraction
  endpoints of ohsome API
• Added ohsome_query() wrapper functions ohsome_extract_contributions(),
  ohsome_contributions_bbox(), ohsome_contributios_centroid() and
  ohsome_contributions_geometry() for contributions extraction endpoints of ohsome
  API
• Added ohsome_query() wrapper functions ohsome_contributions_count() for
  contributions aggregation endpoints of ohsome API
• Added ohsome_query() wrapper function ohsome_users_count() for user
  aggregation endpoints of ohsome API
• ohsome_medata and ohsome_temporalExtent are assigned on loading (not on
  attaching) the package
• ohsome_metadata$extractRegion$temporalExtent and ohsome_temporalExtent are
  no longer converted to POSIXct, but provided as ISO 8601 strings
• Added endpoint-specific check for missing required parameters to query
  validation
• Added validation of JSON response content
• Updated README to reflect new features, added hints on boundary polygon
  acquisition through third-party packages
• Added CITATION file with reference to OSHDB/ohsome API and technical paper