anotherSAS7bdat

Overview

anotherSAS7bdat reads SAS .sas7bdat files into R in configurable chunks using the ReadStat C library by Evan Miller. Each file is opened once, and reading continues between chunks without restarting the parser. Each chunk is an R data frame.

It also converts SAS files directly to one Parquet file with sas7bdat_to_parquet(). Decoded values stay in native buffers and pass through the Arrow C Data Interface to the optional arrow package, without constructing intermediate R data frames or collecting the whole dataset.

Installation

Install the development version from GitHub:

# install.packages("remotes")
remotes::install_github("Fred-Wu/anotherSAS7bdat")

Source installation requires Rtools on Windows, or C++ build tools on macOS and Linux.

For SAS-to-Parquet conversion, also install arrow (version 14.0.0 or later):

install.packages("arrow")

Usage

The package includes three example files generated with SAS 9.4:

• example_uncompressed.sas7bdat: uncompressed.
• example_rle.sas7bdat: RLE compression (COMPRESS=CHAR).
• example_rdc.sas7bdat: RDC compression (COMPRESS=BINARY).

Each contains the same 120 rows with numeric values, Unicode text, dates, times, datetimes, column labels, and ordinary and special missing values. Use any of these filenames in system.file() below. SAS is not needed to read the bundled files.

Reading into R

Both examples below read the entire file into sas_data, an R data frame. The complete dataset and temporary chunks must fit in memory.

For faster binding of many chunks, use data.table::rbindlist() from the optional data.table package in place of do.call(rbind, chunks). It returns a data.table, which also inherits from data.frame.

Using sas7bdat_read():

library(anotherSAS7bdat)

path <- system.file("examples", "example_uncompressed.sas7bdat",
                    package = "anotherSAS7bdat")
chunks <- list()

sas7bdat_read(
  path,
  chunk_rows = 25,
  callback = function(data) {
    chunks[[length(chunks) + 1L]] <<- data
  }
)

sas_data <- do.call(rbind, chunks)
# Faster alternative with data.table installed:
# sas_data <- data.table::rbindlist(chunks, use.names = TRUE)
rm(chunks)

The callback stores each data frame in chunks; rbind combines them into sas_data. The file closes automatically.

Using sas7bdat_open() and sas7bdat_read_chunk():

library(anotherSAS7bdat)

path <- system.file("examples", "example_rle.sas7bdat",
                    package = "anotherSAS7bdat")
reader <- sas7bdat_open(path, chunk_rows = 25)
chunks <- list()

repeat {
  data <- sas7bdat_read_chunk(reader)
  if (is.null(data)) break
  chunks[[length(chunks) + 1L]] <- data
}

sas7bdat_close(reader)

sas_data <- do.call(rbind, chunks)
# Faster alternative with data.table installed:
# sas_data <- data.table::rbindlist(chunks, use.names = TRUE)
rm(chunks)

The loop reads until NULL signals the end of the file, then closes the reader. Use sas7bdat_info(reader) to inspect its current status and reading information.

See ?sas7bdat_read for the reader functions and their settings.

Converting SAS to Parquet

sas7bdat_to_parquet() streams batches into one Parquet file. chunk_rows limits rows per batch; an optional chunk_bytes sets an approximate decoded byte target. The output directory must exist, and existing files are never overwritten. The completed file is published only after conversion succeeds.

library(anotherSAS7bdat)

path <- system.file("examples", "example_rle.sas7bdat",
                    package = "anotherSAS7bdat")
output <- tempfile(fileext = ".parquet")

result <- sas7bdat_to_parquet(
  path,
  output,
  chunk_rows = 100000L,
  compression = "snappy",
  progress = FALSE
)

result$rows       # 120
result$completed  # TRUE

# Read back the small example file.
sas_data <- arrow::read_parquet(output)
head(sas_data)
unlink(output)

Reading back with arrow::read_parquet() collects the output into R. For large output files, use arrow::open_dataset(output) to query the file without collecting the entire dataset.

Recognized SAS dates and datetimes are converted by default; SAS times retain double seconds and are restored as hms when read into R with arrow. Column labels and SAS formats are retained in metadata. Set dates = FALSE to keep the original SAS numeric units. Ordinary and special numeric missing values become Parquet nulls; set missing_tags = TRUE to retain special codes in additional <name>__sas_missing columns.

Set progress = TRUE to show a progress bar; it is enabled by default in interactive R sessions. See ?sas7bdat_to_parquet for all conversion settings and metadata details.

Development Note

This package was developed with assistance from GPT models using OpenAI’s Codex. The overall feature design and logic decisions are mine; GPT models were used to generate and iterate on the implementation.