add readme content

README.md

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 # opensensmapr
-get environmental sensor data from opensensemap.org into R
+This R package ingests data (environmental measurements, sensor stations) from
+the API of opensensemap.org for analysis in R.
+The package aims to be compatible with sf and the tidyverse.
+
+> **Whats up with that package name?** idk, the R people seem to [enjoy][1]
+[dropping][2] [vovels][3] so.. Unfortunately I couldn't fit the naming
+convention to drop an `y` in there.
+
+[1]: https://github.com/tidyverse/readr
+[2]: https://github.com/tidyverse/dplyr
+[3]: https://github.com/tidyverse/tidyr
+
+## Installation
+
+Right now, the package is not on CRAN. To install it from GitHub, run:
+
+```r
+install.packages('devtools')
+devtools::install_github('noerw/opensensmapr')
+```
+
+## Usage
+A usage example is shown in the vignette [`osem-intro`](vignettes/osem-intro.Rmd).
+In general these are the main functions for data retrieval:
+
+```r
+# retrieve a single box by id, or many boxes by some property-filters
+b = osem_box('boxId')
+b = osem_boxes(filter1, filter2, ...)
+
+# get the counts of observed phenomena for a list of boxes
+p = osem_phenomena(b)
+
+# get measurements for a phenomenon
+m = osem_measurements(phenomenon, filter1, ...)
+# get measurements for a phenomenon from selected boxes
+m = osem_measurements(b, phenomenon, filter1, ...)
+# get measurements for a phenomenon from a geographic bounding box
+m = osem_measurements(bbox, phenomenon, filter1, ...)
+
+# get general count statistics of the openSenseMap database
+osem_counts()
+```
+
+Additionally there are some helpers: `summary.sensebox(), plot.sensebox(), osem_as_sf()...`.
+
+For parameter options, open each functions' documentation by calling `?<function-name>`.
+
+## License
+GPL-2.0 - Norwin Roosen