Equivalent functionality with `SQL`
In frab: How to Add Two R Tables

set.seed(0)
knitr::opts_chunk$set(echo = TRUE)
suppressMessages(library("frab"))
suppressMessages(library("sqldf"))

knitr::include_graphics(system.file("help/figures/frab.png", package = "frab"))

One unexpectedly difficult challenge for me developing the frab package is search engine discoverability. Searching for phrases such as "add two tables" or "combine two tables" returns a whole bunch of SQL hits, not the frab package. Part of the problem is that the word "table" means different things to the SQL and R communities. Here I demonstrate that frab functionality [at least for one-dimensional tables] can be replicated using SQL constructs. Consider two simple frab objects and their sum:

(a <- rfrab())
(b <- rfrab())
a+b

We may coerce a and b to a dataframe and combine with rbind():

(ab_df <- rbind(as.data.frame(a),as.data.frame(b)))

However, object ab_df contains repeated key entries. To frabify this, we need to use the group by SQL construct:

aplusb <- sqldf('
SELECT key, sum(value) AS value
FROM  ab_df
GROUP BY key
')
aplusb

(Note that the above construction would require a little polishing for production use as zeros are not removed automatically). However, the resulting data frame can be coerced back to frab form: