Fit models inside the database. modeldb works with most databases back-ends because it leverages dplyr and dbplyr for the final SQL translation of the algorithm. It currently supports:

  • K-means clustering

  • Linear regression

Installation

Install the CRAN version with:

# install.packages("modeldb")

The development version is available using devtools as follows:

# install.packages("remotes")
# remotes::install_github("tidymodels/modeldb")

Linear regression

An easy way to try out the package is by creating a temporary SQLite database, and loading mtcars to it

con <- DBI::dbConnect(RSQLite::SQLite(), path = ":memory:")
RSQLite::initExtension(con)
dplyr::copy_to(con, mtcars)
library(dplyr)

tbl(con, "mtcars") %>%
  select(wt, mpg, qsec) %>%
  linear_regression_db(wt)
## # A tibble: 1 x 3
##   `(Intercept)`    mpg  qsec
##           <dbl>  <dbl> <dbl>
## 1          4.12 -0.156 0.125

The model output can be parsed by tidypredict to run the predictions in the database. Please see the Linear Regression article to learn more about how to use linear_regression_db()

K Means clustering

To use the simple_kmeans_db() function, simply pipe the database back end table to the function. This returns a list object that contains two items:

  • A sql query table with the final center assignment
  • A local table with the information about the centers
km <- tbl(con, "mtcars") %>%
  simple_kmeans_db(mpg, wt)

colnames(km)
##  [1] "k_center" "k_mpg"    "k_wt"     "mpg"      "cyl"      "disp"    
##  [7] "hp"       "drat"     "wt"       "qsec"     "vs"       "am"      
## [13] "gear"     "carb"

The SQL statement from tbl can be extracted using dbplyr’s remote_query()

dbplyr::remote_query(km)
## <SQL> SELECT `RHS`.`center` AS `k_center`, `LHS`.`k_mpg` AS `k_mpg`, `LHS`.`k_wt` AS `k_wt`, `RHS`.`mpg` AS `mpg`, `RHS`.`cyl` AS `cyl`, `RHS`.`disp` AS `disp`, `RHS`.`hp` AS `hp`, `RHS`.`drat` AS `drat`, `RHS`.`wt` AS `wt`, `RHS`.`qsec` AS `qsec`, `RHS`.`vs` AS `vs`, `RHS`.`am` AS `am`, `RHS`.`gear` AS `gear`, `RHS`.`carb` AS `carb`
## FROM (SELECT `center` AS `k_center`, `mpg` AS `k_mpg`, `wt` AS `k_wt`
## FROM (SELECT `center`, AVG(`mpg`) AS `mpg`, AVG(`wt`) AS `wt`
## FROM (SELECT `mpg`, `wt`, `center`
## FROM (SELECT *
## FROM (SELECT `mpg`, `cyl`, `disp`, `hp`, `drat`, `wt`, `qsec`, `vs`, `am`, `gear`, `carb`, `center_1`, `center_2`, `center_3`, CASE
## WHEN (`center_1` >= `center_1` AND `center_1` < `center_2` AND `center_1` < `center_3`) THEN ('center_1')
## WHEN (`center_2` < `center_1` AND `center_2` >= `center_2` AND `center_2` < `center_3`) THEN ('center_2')
## WHEN (`center_3` < `center_1` AND `center_3` < `center_2` AND `center_3` >= `center_3`) THEN ('center_3')
## END AS `center`
## FROM (SELECT `mpg`, `cyl`, `disp`, `hp`, `drat`, `wt`, `qsec`, `vs`, `am`, `gear`, `carb`, SQRT(((20.6428571428571 - `mpg`) * (20.6428571428571 - `mpg`)) + ((3.07214285714286 - `wt`) * (3.07214285714286 - `wt`))) AS `center_1`, SQRT(((14.4583333333333 - `mpg`) * (14.4583333333333 - `mpg`)) + ((4.05866666666667 - `wt`) * (4.05866666666667 - `wt`))) AS `center_2`, SQRT(((30.0666666666667 - `mpg`) * (30.0666666666667 - `mpg`)) + ((1.873 - `wt`) * (1.873 - `wt`))) AS `center_3`
## FROM `mtcars`))
## WHERE (NOT(((`center`) IS NULL)))))
## GROUP BY `center`)) AS `LHS`
## RIGHT JOIN (SELECT `mpg`, `cyl`, `disp`, `hp`, `drat`, `wt`, `qsec`, `vs`, `am`, `gear`, `carb`, `center`
## FROM (SELECT `mpg`, `cyl`, `disp`, `hp`, `drat`, `wt`, `qsec`, `vs`, `am`, `gear`, `carb`, `center_1`, `center_2`, `center_3`, CASE
## WHEN (`center_1` >= `center_1` AND `center_1` < `center_2` AND `center_1` < `center_3`) THEN ('center_1')
## WHEN (`center_2` < `center_1` AND `center_2` >= `center_2` AND `center_2` < `center_3`) THEN ('center_2')
## WHEN (`center_3` < `center_1` AND `center_3` < `center_2` AND `center_3` >= `center_3`) THEN ('center_3')
## END AS `center`
## FROM (SELECT `mpg`, `cyl`, `disp`, `hp`, `drat`, `wt`, `qsec`, `vs`, `am`, `gear`, `carb`, SQRT(((20.6428571428571 - `mpg`) * (20.6428571428571 - `mpg`)) + ((3.07214285714286 - `wt`) * (3.07214285714286 - `wt`))) AS `center_1`, SQRT(((14.4583333333333 - `mpg`) * (14.4583333333333 - `mpg`)) + ((4.05866666666667 - `wt`) * (4.05866666666667 - `wt`))) AS `center_2`, SQRT(((30.0666666666667 - `mpg`) * (30.0666666666667 - `mpg`)) + ((1.873 - `wt`) * (1.873 - `wt`))) AS `center_3`
## FROM `mtcars`))
## WHERE (NOT(((`center`) IS NULL)))) AS `RHS`
## ON (`LHS`.`k_center` = `RHS`.`center`)