Extracts the origin of a HDD object

Use this function to extract the information on how the HDD data set was created.

origin(x)

Arguments

x

A HDD object.

Value

A character vector, if the HDD data set has been created with several instances of write_hdd its length will be greater than 1.

Details

Each HDD lives on disk and a “_hdd.txt” is always present in the folder containing summary information. The function origin extracts the log from this information file.

See also

See hdd, sub-.hdd and cash-.hdd for the extraction and manipulation of out of memory data. For importation of HDD data sets from text files: see txt2hdd.

See hdd_slice to apply functions to chunks of data (and create HDD objects) and hdd_merge to merge large files.

To create/reshape HDD objects from memory or from other HDD objects, see write_hdd.

To display general information from HDD objects: origin, summary.hdd, print.hdd, dim.hdd and names.hdd.

Examples

# Toy example with iris data

hdd_path = tempfile()
write_hdd(iris, hdd_path, rowsPerChunk = 20)

base_hdd = hdd(hdd_path)
origin(base_hdd)
#> [1] "# 1-8 ; 150 rows ; write_hdd(x = iris, dir = hdd_path, rowsPerChunk = 20)"

# Let's add something
write_hdd(head(iris), hdd_path, add = TRUE)
write_hdd(iris, hdd_path, add = TRUE, rowsPerChunk = 50)

base_hdd = hdd(hdd_path)
origin(base_hdd)
#> [1] "# 1-8 ; 150 rows ; write_hdd(x = iris, dir = hdd_path, rowsPerChunk = 20)"              
#> [2] "# 9 ; 6 rows ; write_hdd(x = head(iris), dir = hdd_path, add = TRUE)"                   
#> [3] "# 10-12 ; 150 rows ; write_hdd(x = iris, dir = hdd_path, rowsPerChunk = 50, add = TRUE)"