A way to use `dplyr`'s `join` functions to extract data from a lookup table

lookup_tables.Rmd

---
title: "Lookup Tables"
output:
  html_document:
    toc: true
    toc_float: true
---


```{r setup, include=FALSE}
pkg <- c("dplyr", "DT")

new.pkg <- pkg[!(pkg %in% installed.packages())]

if (length(new.pkg)) {
  install.packages(new.pkg, repos = "http://cran.rstudio.com")
}

lapply(pkg, library, character.only = TRUE)
```

```{r}
set.seed(1)    # for reproducible example
n <- 100
groups <- c("V", "W", "X", "Y")
colors <- c("green", "red", "blue", "black")
sizes <- c("small", "medium", "large")
df <- data_frame(
  group = sample(groups, size = n, replace = TRUE),
  color = sample(colors, size = n, replace = TRUE),
  size = sample(sizes, size = n, replace = TRUE)
)

lookup_table <- data.frame(
  expand.grid(groups, colors, sizes, stringsAsFactors = FALSE)
)
lookup_table <- lookup_table %>%
  rename(group = Var1, color = Var2, size = Var3) %>%
  mutate(value = sample(1:nrow(lookup_table), size = nrow(lookup_table), replace = FALSE))

merged <- inner_join(df, lookup_table, by = c("group", "color", "size"))
```

```{r output_table}
datatable(df)
datatable(lookup_table)
datatable(merged)
```