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< title > Caching openSenseMap Data for Reproducibility< / title >
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< body >
< h1 class = "title toc-ignore" > Caching openSenseMap Data for
Reproducibility< / h1 >
< h4 class = "author" > Norwin Roosen< / h4 >
< h4 class = "date" > 2023-03-08< / h4 >
< p > It may be useful to download data from openSenseMap only once. For
reproducible results, the data should be saved to disk, and reloaded at
a later point.< / p >
< p > This avoids..< / p >
< ul >
< li > changed results for queries without date parameters,< / li >
< li > unnecessary wait times,< / li >
< li > risk of API changes / API unavailability,< / li >
< li > stress on the openSenseMap-server.< / li >
< / ul >
< p > This vignette shows how to use this built in
< code > opensensmapr< / code > feature, and how to do it yourself in case you
want to save to other data formats.< / p >
< div class = "sourceCode" id = "cb1" > < pre class = "sourceCode r" > < code class = "sourceCode r" > < span id = "cb1-1" > < a href = "#cb1-1" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "co" > # this vignette requires:< / span > < / span >
< span id = "cb1-2" > < a href = "#cb1-2" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "fu" > library< / span > (opensensmapr)< / span >
< span id = "cb1-3" > < a href = "#cb1-3" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "fu" > library< / span > (jsonlite)< / span >
< span id = "cb1-4" > < a href = "#cb1-4" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "fu" > library< / span > (readr)< / span > < / code > < / pre > < / div >
< div id = "using-the-opensensmapr-caching-feature" class = "section level2" >
< h2 > Using the opensensmapr Caching Feature< / h2 >
< p > All data retrieval functions of < code > opensensmapr< / code > have a
built in caching feature, which serializes an API response to disk.
Subsequent identical requests will then return the serialized data
instead of making another request.< / p >
< p > To use this feature, just add a path to a directory to the
< code > cache< / code > parameter:< / p >
< div class = "sourceCode" id = "cb2" > < pre class = "sourceCode r" > < code class = "sourceCode r" > < span id = "cb2-1" > < a href = "#cb2-1" aria-hidden = "true" tabindex = "-1" > < / a > b < span class = "ot" > =< / span > < span class = "fu" > osem_boxes< / span > (< span class = "at" > grouptag =< / span > < span class = "st" > ' ifgi' < / span > , < span class = "at" > cache =< / span > < span class = "fu" > tempdir< / span > ())< / span >
< span id = "cb2-2" > < a href = "#cb2-2" aria-hidden = "true" tabindex = "-1" > < / a > < / span >
< span id = "cb2-3" > < a href = "#cb2-3" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "co" > # the next identical request will hit the cache only!< / span > < / span >
< span id = "cb2-4" > < a href = "#cb2-4" aria-hidden = "true" tabindex = "-1" > < / a > b < span class = "ot" > =< / span > < span class = "fu" > osem_boxes< / span > (< span class = "at" > grouptag =< / span > < span class = "st" > ' ifgi' < / span > , < span class = "at" > cache =< / span > < span class = "fu" > tempdir< / span > ())< / span >
< span id = "cb2-5" > < a href = "#cb2-5" aria-hidden = "true" tabindex = "-1" > < / a > < / span >
< span id = "cb2-6" > < a href = "#cb2-6" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "co" > # requests without the cache parameter will still be performed normally< / span > < / span >
< span id = "cb2-7" > < a href = "#cb2-7" aria-hidden = "true" tabindex = "-1" > < / a > b < span class = "ot" > =< / span > < span class = "fu" > osem_boxes< / span > (< span class = "at" > grouptag =< / span > < span class = "st" > ' ifgi' < / span > )< / span > < / code > < / pre > < / div >
< p > Looking at the cache directory we can see one file for each request,
which is identified through a hash of the request URL:< / p >
< div class = "sourceCode" id = "cb3" > < pre class = "sourceCode r" > < code class = "sourceCode r" > < span id = "cb3-1" > < a href = "#cb3-1" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "fu" > list.files< / span > (< span class = "fu" > tempdir< / span > (), < span class = "at" > pattern =< / span > < span class = "st" > ' osemcache< / span > < span class = "sc" > \\< / span > < span class = "st" > ..*< / span > < span class = "sc" > \\< / span > < span class = "st" > .rds' < / span > )< / span > < / code > < / pre > < / div >
< pre > < code > ## [1] " osemcache.17db5c57fc6fca4d836fa2cf30345ce8767cd61a.rds" < / code > < / pre >
< p > You can maintain multiple caches simultaneously which allows to only
store data related to a script in the same directory:< / p >
< div class = "sourceCode" id = "cb5" > < pre class = "sourceCode r" > < code class = "sourceCode r" > < span id = "cb5-1" > < a href = "#cb5-1" aria-hidden = "true" tabindex = "-1" > < / a > cacheDir < span class = "ot" > =< / span > < span class = "fu" > getwd< / span > () < span class = "co" > # current working directory< / span > < / span >
< span id = "cb5-2" > < a href = "#cb5-2" aria-hidden = "true" tabindex = "-1" > < / a > b < span class = "ot" > =< / span > < span class = "fu" > osem_boxes< / span > (< span class = "at" > grouptag =< / span > < span class = "st" > ' ifgi' < / span > , < span class = "at" > cache =< / span > cacheDir)< / span >
< span id = "cb5-3" > < a href = "#cb5-3" aria-hidden = "true" tabindex = "-1" > < / a > < / span >
< span id = "cb5-4" > < a href = "#cb5-4" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "co" > # the next identical request will hit the cache only!< / span > < / span >
< span id = "cb5-5" > < a href = "#cb5-5" aria-hidden = "true" tabindex = "-1" > < / a > b < span class = "ot" > =< / span > < span class = "fu" > osem_boxes< / span > (< span class = "at" > grouptag =< / span > < span class = "st" > ' ifgi' < / span > , < span class = "at" > cache =< / span > cacheDir)< / span > < / code > < / pre > < / div >
< p > To get fresh results again, just call < code > osem_clear_cache()< / code >
for the respective cache:< / p >
< div class = "sourceCode" id = "cb6" > < pre class = "sourceCode r" > < code class = "sourceCode r" > < span id = "cb6-1" > < a href = "#cb6-1" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "fu" > osem_clear_cache< / span > () < span class = "co" > # clears default cache< / span > < / span >
< span id = "cb6-2" > < a href = "#cb6-2" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "fu" > osem_clear_cache< / span > (< span class = "fu" > getwd< / span > ()) < span class = "co" > # clears a custom cache< / span > < / span > < / code > < / pre > < / div >
< / div >
< div id = "custom-de--serialization" class = "section level2" >
< h2 > Custom (De-) Serialization< / h2 >
< p > If you want to roll your own serialization method to support custom
data formats, here’ < / p >
< div class = "sourceCode" id = "cb7" > < pre class = "sourceCode r" > < code class = "sourceCode r" > < span id = "cb7-1" > < a href = "#cb7-1" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "co" > # first get our example data:< / span > < / span >
< span id = "cb7-2" > < a href = "#cb7-2" aria-hidden = "true" tabindex = "-1" > < / a > measurements < span class = "ot" > =< / span > < span class = "fu" > osem_measurements< / span > (< span class = "st" > ' Windgeschwindigkeit' < / span > )< / span > < / code > < / pre > < / div >
< p > If you are paranoid and worry about < code > .rds< / code > files not being
decodable anymore in the (distant) future, you could serialize to a
plain text format such as JSON. This of course comes at the cost of
storage space and performance.< / p >
< div class = "sourceCode" id = "cb8" > < pre class = "sourceCode r" > < code class = "sourceCode r" > < span id = "cb8-1" > < a href = "#cb8-1" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "co" > # serializing senseBoxes to JSON, and loading from file again:< / span > < / span >
< span id = "cb8-2" > < a href = "#cb8-2" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "fu" > write< / span > (jsonlite< span class = "sc" > ::< / span > < span class = "fu" > serializeJSON< / span > (measurements), < span class = "st" > ' measurements.json' < / span > )< / span >
< span id = "cb8-3" > < a href = "#cb8-3" aria-hidden = "true" tabindex = "-1" > < / a > measurements_from_file < span class = "ot" > =< / span > jsonlite< span class = "sc" > ::< / span > < span class = "fu" > unserializeJSON< / span > (readr< span class = "sc" > ::< / span > < span class = "fu" > read_file< / span > (< span class = "st" > ' measurements.json' < / span > ))< / span >
< span id = "cb8-4" > < a href = "#cb8-4" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "fu" > class< / span > (measurements_from_file)< / span > < / code > < / pre > < / div >
< p > This method also persists the R object metadata (classes,
attributes). If you were to use a serialization method that can’
persist object metadata, you could re-apply it with the following
functions:< / p >
< div class = "sourceCode" id = "cb9" > < pre class = "sourceCode r" > < code class = "sourceCode r" > < span id = "cb9-1" > < a href = "#cb9-1" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "co" > # note the toJSON call instead of serializeJSON< / span > < / span >
< span id = "cb9-2" > < a href = "#cb9-2" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "fu" > write< / span > (jsonlite< span class = "sc" > ::< / span > < span class = "fu" > toJSON< / span > (measurements), < span class = "st" > ' measurements_bad.json' < / span > )< / span >
< span id = "cb9-3" > < a href = "#cb9-3" aria-hidden = "true" tabindex = "-1" > < / a > measurements_without_attrs < span class = "ot" > =< / span > jsonlite< span class = "sc" > ::< / span > < span class = "fu" > fromJSON< / span > (< span class = "st" > ' measurements_bad.json' < / span > )< / span >
< span id = "cb9-4" > < a href = "#cb9-4" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "fu" > class< / span > (measurements_without_attrs)< / span >
< span id = "cb9-5" > < a href = "#cb9-5" aria-hidden = "true" tabindex = "-1" > < / a > < / span >
< span id = "cb9-6" > < a href = "#cb9-6" aria-hidden = "true" tabindex = "-1" > < / a > measurements_with_attrs < span class = "ot" > =< / span > < span class = "fu" > osem_as_measurements< / span > (measurements_without_attrs)< / span >
< span id = "cb9-7" > < a href = "#cb9-7" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "fu" > class< / span > (measurements_with_attrs)< / span > < / code > < / pre > < / div >
< p > The same goes for boxes via < code > osem_as_sensebox()< / code > .< / p >
< / div >
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