R Under development (unstable) (2024-01-23 r85822 ucrt) -- "Unsuffered Consequences"
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> source("incl/start.R")
Loading required package: R.oo
Loading required package: R.methodsS3
R.methodsS3 v1.8.2 (2022-06-13 22:00:14 UTC) successfully loaded. See ?R.methodsS3 for help.
R.oo v1.26.0 successfully loaded. See ?R.oo for help.

Attaching package: 'R.oo'

The following object is masked from 'package:R.methodsS3':

    throw

The following objects are masked from 'package:methods':

    getClasses, getMethods

The following objects are masked from 'package:base':

    attach, detach, load, save

R.filesets v2.15.1 successfully loaded. See ?R.filesets for help.

Attaching package: 'R.filesets'

The following objects are masked from 'package:base':

    append, readLines

> 
> library("R.utils")  # writeDataFrame()
R.utils v2.12.3 (2023-11-18 01:00:02 UTC) successfully loaded. See ?R.utils for help.

Attaching package: 'R.utils'

The following objects are masked _by_ '.GlobalEnv':

    mstr, printf

The following object is masked from 'package:R.filesets':

    validate

The following object is masked from 'package:utils':

    timestamp

The following objects are masked from 'package:base':

    cat, commandArgs, getOption, isOpen, nullfile, parse, use, warnings

> 
> message("*** A huge TabularTextFile")
*** A huge TabularTextFile
> 
> # Generate a large data frame
> set.seed(42)
> n <- 1e5
> data <- data.frame(
+   index = seq_len(n),
+   x = runif(n),
+   y = rnorm(n),
+   symbol = sample(letters, size=n, replace=TRUE)
+ )
> 
> # Write to tab-delimited file
> pathname <- tempfile(fileext=".tsv")
> writeDataFrame(data, file=pathname)
> 
> # Setup tabular file
> db <- TabularTextFile(pathname)
> print(db)
TabularTextFile:
Name: file8fac623a8f
Tags: 
Full name: file8fac623a8f
Pathname: D:/temp/RtmpGU8PUf/file8fac623a8f.tsv
File size: 4.30 MiB (4505234 bytes)
Number of data rows: 100000
Columns [4]: 'index', 'x', 'y', 'symbol'
Number of text lines: 100006
> 
> # Read subset of the rows
> n <- nbrOfRows(db)
> data2 <- readDataFrame(db, rows=seq(from=1, to=n, length.out=0.10*n))
> str(data2)
'data.frame':	10000 obs. of  4 variables:
 $ index : int  1 11 21 31 41 51 61 71 81 91 ...
 $ x     : num  0.915 0.458 0.904 0.738 0.38 ...
 $ y     : num  0.526 0.614 0.577 -0.483 -0.888 ...
 $ symbol: chr  "s" "e" "j" "f" ...
> 
> # Cleanup
> file.remove(pathname)
[1] TRUE
> 
> source("incl/end.R")
> 
> proc.time()
   user  system elapsed 
   7.81   33.76   42.54