dbpf_observations_agg: Return statistics about observations in DB

In geocryology/PermafrostDB: PermafrostDB

Return statistics about observations in DB

Description

Provides mean min max and count for a certain period and one or several locations.

Usage

dbpf_observations_agg(
  con,
  location_name,
  unit_of_measurement = "C",
  period = 1,
  time_b = "1950-01-01 00:00:00+00",
  time_e = "2050-01-01 00:00:00+00",
  verbose = FALSE,
  fetch = FALSE,
  n = 1e+05
)

Arguments

con	Database connection object, as returned by dbpf_con()
location_name	Character string or list of several with the location name(s) to be queried for.
unit_of_measurement	Unit of measurments, defaults to "C". Used to identify the observation time - see Details.
period	Period over wich to aggregate time series [h], defaults to one hour (period = 1).
time_b	Begin time for the interval to be analysed. Use the format "1950-01-01 00:00:00+00"
time_e	End time for the interval to be analysed. Use the format "1950-01-01 00:00:00+00"
verbose	Provide terminal output of the query string? (defaults to FALSE)
fetch	Whether to return results incrementally using dbSendQuery & dbFetch(), otherwise downloads them all at once using dbGetQuery(). Defaults to FALSE.
n	if fetch == TRUE, then specifies the number of rows to download in each batch. Ignored if fetch == FALSE.

Details

These simple functions return all data as data frames. When making a query many times, optimise the SQL statement to only request the data you actually need. Details of aggregation: The aggregation is based on a new column calculated based on the number of seconds elapsed since 1970-01-01 00:00:00 UTC (referred to as 'epoch'). The rounding [FLOOR(epoch/period/3600) * period * 3600] thereby references all values of a period to the time when this period begins. For example, a daily average (period = 24) will include all values between 2016-11-01 00:00:00 and 2016-11-02 23:59:59 under the timestamp 2016-11-01 00:00:00.

The unit_of_measurement variable is used to distinguish between different measurement types. The default (C) will return observations that measure temperature in degrees celsius. To obtain observations of relative humidity, use "

When performing large queries (millions of rows), it is recommended to set fetch = TRUE. Otherwise R can run into trouble.

Value

Data frame with locations in rows and columns loc_name, height, max, min, avg, cnt

Author(s)

Stephan Gruber <[e-mail]>

Examples

## Not run: 
con <- dbpf_con()
dbpf_observations_agg(con, "NGO-RC-163_ST01", period = 24)
dbDisconnect(con)

## End(Not run)

geocryology/PermafrostDB documentation built on April 17, 2025, 11:54 a.m.