Retrieving data in R¶

We provide an R function, query, that fetches time series data from InfluxDB server and returns data.frame object.

Setting up¶

The query function uses httr, an HTTP client library for R. Please install its ssl dependency beforehand. On Debian-based systems:

$ sudo apt-get install libssl-dev

Assuming that you’ve already installed r-base and RStudio (external instructions), you need to install httr. Please execute the following inside your RStudio environment to install httr:

> install.packages("httr")

We need two additional packages for the demonstration, devtools to fetch the query source code (api-v1.3.r) from our gist repository and optional data.table to cast the data into columns. Of course, you can skip this step, and download the source code into your environment.

> install.packages("devtools")
> install.packages("data.table")

Provided function¶

query(…)

Download¶

to download the source of api-v1.3.r, please use the Raw or Download ZIP button on the GitHubGist page

Description¶

fetches time series data with matching parameters from the database server and converts into data.frame object

Usage¶

query(domain, apiKey, timeFilter = "", device = "//", location = "//", sensor = "//", includeNetworkSensors = FALSE, channel = "//", aggFunc = "", aggInterval = "", doCast = TRUE, castAggFunc = mean, convertTimestamp = TRUE, timezone = "UTC")

Arguments¶

domain
The domain part of the URL

apiKey
Secret key for authenticating with the server

timeFilter
Time filter expression written in InfluxQL, the default value "" ignores time

device
InfluxQL regular expression to select devices, the default value "//" matches all devices

location
InfluxQL regular expression to select locations, the default value "//" matches all locations

sensor
InfluxQL regular expression to select sensors, the default value "//" matches all sensors

includeNetworkSensors

TRUE
allows returning network-related data

FALSE (default)
filters out all network-related data

channel
InfluxQL regular expression to select channels, the default value "//" matches all channels

aggFunc
InfluxQL aggregate function evaluated on the selected data, no aggregate function is applied by default

aggInterval
InfluxQL time interval value, used with aggFunc

doCast

TRUE (default)
return time series into individual columns,

FALSE
return all time series in a single column

castAggFunc
Apply aggregate function when casting data, by default mean function is applied

convertTimestamp

TRUE (default)
convert timestamps into date time objects,

FALSE
return timestamps in unix time in milliseconds

timezone
Timezone name, used with convertTimestamp

Value¶

data.frame object containing time series data

Demonstration script¶

The following R script demonstrates the main functionality of query function with our demo.decentlab.com server. In this script, we use the previously installed devtools to source query from our gist repository and enable casting so that the output data can be column oriented. Please note that the casting requires the data.table package.

library(devtools)
devtools::source_gist('79f52bef3778e0dbbd5dc58437621d88',
                      filename = 'api-v1.3.r')

Please remove the filename parameter if above command fails.

data.df <- query(
  domain = "demo.decentlab.com",
  apiKey = "eyJrIjoiclhMRFFvUXFzQXpKVkZydm52b0VMRVg3M3U2b3VqQUciLCJuIjoiZGF0YS1xdWVyeS1hcGktZGVtby0yIiwiaWQiOjF9",
  timeFilter = "time > '2020-01-01' AND time < '2020-01-05'",
  device = "/^(3001|6414)$/",
  sensor = "/sht30|mb7389/",
  aggFunc = "mean",
  aggInterval = "12h",
)

The above example will retrieve the data from demo.decentlab.com server, matching the following criteria:

devices with ID 3001 or 6414

sensor names containing either sht30 or mb7389

compute the mean of groups divided by 12-hour interval

received between 2020-01-01 and 2020-01-05

The value of data.df:

> head(data.df)
                time 3001.sensirion-sht30-humidity 3001.sensirion-sht30-temperature 6414.maxbotix-mb7389-distance
2020-01-01 00:00:00                      31.61432                         20.87331                      3189.880
2020-01-01 12:00:00                      31.19008                         20.90538                      3184.826
2020-01-02 00:00:00                      30.88009                         20.86234                      3194.190
2020-01-02 12:00:00                      30.75082                         20.89822                      3188.148
2020-01-03 00:00:00                      30.78512                         20.87438                      3192.785
2020-01-03 12:00:00                      31.26576                         21.04921                      3182.441
maxbotix-mb7389-trials
                        15
                        15
                        15
                        15
                        15
                        15

Note that the head function shows only the first six rows.