# qsave Saves (serializes) an object to disk. ```r qsave(x, file, preset = "high", algorithm = "zstd", compress_level = 4L, shuffle_control = 15L, check_hash=TRUE, nthreads = 1) ``` ## Arguments - `x`: The object to serialize. - `file`: The file name/path. - `preset`: One of `"fast"`, `"balanced"`, `"high"` (default), `"archive"`, `"uncompressed"` or `"custom"`. See section **Presets** for details. - `algorithm`: Ignored unless ‘preset = "custom"’. Compression algorithm used: `"lz4"`, `"zstd"`, `"lz4hc"`, `"zstd_stream"` or `"uncompressed"`. - `compress_level`: Ignored unless ‘preset = "custom"’. The compression level used. For lz4, this number must be > 1 (higher is less compressed). For zstd, a number between `-50` to `22` (higher is more compressed). Due to the format of qs, there is very little benefit to compression levels > 5 or so. - `shuffle_control`: Ignored unless ‘preset = "custom"’. An integer setting the use of byte shuffle compression. A value between `0` and `15` (default `15`). See section **Byte shuffling** for details. - `check_hash`: Default `TRUE`, compute a hash which can be used to verify file integrity during serialization. - `nthreads`: Number of threads to use. Default `1`. ## Returns The total number of bytes written to the file (returned invisibly). ## Details This function serializes and compresses R objects using block compression with the option of byte shuffling. ## Presets There are lots of possible parameters. To simplify usage, there are four main presets that are performant over a large variety of data: * ‘"fast"’ is a shortcut for `algorithm = "lz4"`, `compress_level = 100` and `shuffle_control = 0`. * ‘"balanced"’ is a shortcut for `algorithm = "lz4"`, `compress_level = 1` and `shuffle_control = 15`. * ‘"high"’ is a shortcut for `algorithm = "zstd"`, `compress_level = 4` and `shuffle_control = 15`. * ‘"archive"’ is a shortcut for `algorithm = "zstd_stream"`, `compress_level = 14` and `shuffle_control = 15`. (`zstd_stream` is currently single-threaded only) To gain more control over compression level and byte shuffling, set `preset = "custom"`, in which case the individual parameters `algorithm`, `compress_level` and `shuffle_control` are actually regarded. ## Byte shuffling The parameter `shuffle_control` defines which numerical R object types are subject to **byte shuffling**. Generally speaking, the more ordered/sequential an object is (e.g., `1:1e7`), the larger the potential benefit of byte shuffling. It is not uncommon to improve compression ratio or compression speed by several orders of magnitude. The more random an object is (e.g., `rnorm(1e7)`), the less potential benefit there is, even negative benefit is possible. Integer vectors almost always benefit from byte shuffling, whereas the results for numeric vectors are mixed. To control block shuffling, add +1 to the parameter for logical vectors, +2 for integer vectors, +4 for numeric vectors and/or +8 for complex vectors. ## Examples ```r x <- data.frame(int = sample(1e3, replace=TRUE), num = rnorm(1e3), char = sample(starnames$`IAU Name`, 1e3, replace=TRUE), stringsAsFactors = FALSE) myfile <- tempfile() qsave(x, myfile) x2 <- qread(myfile) identical(x, x2) # returns true # qs support multithreading qsave(x, myfile, nthreads=2) x2 <- qread(myfile, nthreads=2) identical(x, x2) # returns true # Other examples z <- 1:1e7 myfile <- tempfile() qsave(z, myfile) z2 <- qread(myfile) identical(z, z2) # returns true w <- as.list(rnorm(1e6)) myfile <- tempfile() qsave(w, myfile) w2 <- qread(myfile) identical(w, w2) # returns true ```

qsave function