introduction.R
In rPref: Database Preferences and Skyline Computation

## ---- echo = FALSE, message = FALSE-------------------------------------------
library(rPref)
suppressPackageStartupMessages(library(dplyr))

## ---- results='asis'----------------------------------------------------------
p <- high(mpg) * high(hp)
res <- psel(mtcars, p)
knitr::kable(select(res, mpg, hp))

## ---- collapse = TRUE---------------------------------------------------------
p <- high(mpg, df = mtcars) * high(hp) * low(qsec)
p

## ---- results='asis'----------------------------------------------------------
res <- peval(p)
knitr::kable(select(res, mpg, hp, qsec))

## ---- results='asis'----------------------------------------------------------
res <- mtcars %>% filter(am == 0) %>% psel(p)
knitr::kable(select(res, am, mpg, hp, qsec))

## -----------------------------------------------------------------------------
p <- true(am == 1) & high(gear)

## ---- results='asis'----------------------------------------------------------
res <- psel(mtcars, p)
knitr::kable(select(res, am, gear, hp, cyl))

## ---- results='asis'----------------------------------------------------------
p <- (true(am == 1) & high(gear)) * high(hp/cyl)
res <- psel(mtcars, p)
knitr::kable(select(res, am, gear, hp, cyl))

## ---- results='asis'----------------------------------------------------------
res <- psel(mtcars, p, top = 3)
knitr::kable(select(res, am, gear, hp, cyl, .level))

## ---- results='asis'----------------------------------------------------------
res <- psel(mtcars, p, at_least = 3)
knitr::kable(select(res, am, gear, hp, cyl, .level))

## ---- results='asis'----------------------------------------------------------
grouped_df <- group_by(mtcars, cyl)
res <- psel(grouped_df, high(hp) * high(mpg))
knitr::kable(select(res, cyl, hp, mpg))