Update README.md

README.md

@@ -26,21 +26,22 @@
 [ReadStatTables.jl](https://github.com/junyuan-chen/ReadStatTables.jl)
 is a Julia package for reading data files from Stata, SAS and SPSS into
 a [Tables.jl](https://github.com/JuliaData/Tables.jl)-compatible table.
-It relies on [ReadStat.jl](https://github.com/queryverse/ReadStat.jl),
-which is a Julia interface of the
-[ReadStat](https://github.com/WizardMac/ReadStat) C library,
+It utilizes the [ReadStat](https://github.com/WizardMac/ReadStat) C library
+developed by [Evan Miller](https://www.evanmiller.org)
 for parsing the data files.
-The same C library is also the backend
-for popular packages such as [pyreadstat](https://github.com/Roche/pyreadstat)
-and [haven](https://github.com/tidyverse/haven).
+The same C library is also the backend of popular packages in other languages such as
+[pyreadstat](https://github.com/Roche/pyreadstat) for Python
+and [haven](https://github.com/tidyverse/haven) for R.
+ReadStatTables.jl can be viewed as the Julia counterpart for similar purposes.
 
 ## Features
 
-ReadStatTables.jl adds the following features on top of the read support
-from [ReadStat.jl](https://github.com/queryverse/ReadStat.jl).
+ReadStatTables.jl provides the following features in addition to
+wrapping the C interface of ReadStat.
 
-- A lightweight [Tables.jl](https://github.com/JuliaData/Tables.jl)-compatible column table `ReadStatTable` for basic operations.
-- Integration of value labels via a customized array type `LabeledArray`.
+- Efficient data collection from ReadStat parser to a [Tables.jl](https://github.com/JuliaData/Tables.jl)-compatible column table `ReadStatTable`.
+- Interface of file-level and variable-level metadata compatible with [DataAPI.jl](https://github.com/JuliaData/DataAPI.jl).
+- Integration of value labels into data columns via a customized array type `LabeledArray`.
 - Translation of date and time values into Julia time types `Date` and `DateTime`.
 
 ## Quick Start
@@ -66,7 +67,7 @@ To access a column from the above table:
 
 ```julia
 julia> tb.myord
-5-element LabeledVector{Union{Missing, Int8}, LabeledValue{Union{Missing, Int8}}}:
+5-element LabeledVector{Union{Missing, Int8}, Vector{Union{Missing, Int8}}, Union{Char, Int32}}:
  1 => low
  2 => medium
  3 => high
@@ -75,20 +76,31 @@ julia> tb.myord
 ```
 
 Notice that for data variables with value labels,
-both the original values and the labels are preserved.
+both the original values and the value labels are preserved.
 
-To access metadata including variable labels:
+File-level and variable-level metadata can be retrieved and modified
+via methods compatible with [DataAPI.jl](https://github.com/JuliaData/DataAPI.jl):
 
 ```julia
-julia> getmeta(tb)
+julia> metadata(tb)
 ReadStatMeta:
-  variable labels:    Dict(:myord => "ordinal", :mynum => "numeric", :mydate => "date", :mychar => "character", :dtime => "datetime", :mytime => "time", :mylabl => "labeled")
-  variable formats:   Dict(:myord => "%16.0f", :mynum => "%16.2f", :mydate => "%td", :mychar => "%-1s", :dtime => "%tc", :mytime => "%tcHH:MM:SS", :mylabl => "%16.0f")
-  value label names:  Dict(:myord => "myord", :mynum => "", :mydate => "", :mychar => "", :dtime => "", :mytime => "", :mylabl => "mylabl")
-  value labels:       Dict{String, Dict{Any, String}}("myord" => Dict(2 => "medium", 3 => "high", 1 => "low"), "mylabl" => Dict(2 => "Female", 1 => "Male"))
-  file label:         A test file
-  file timestamp:     2021-04-23T04:36:00
-  file extension:     .dta
+  row count           => 5
+  var count           => 7
+  modified time       => 2021-04-23T04:36:00
+  file format version => 118
+  file label          => A test file
+  file extension      => .dta
+
+julia> colmetadata(tb, :mylabl)
+ReadStatColMeta:
+  label         => labeled
+  format        => %16.0f
+  type          => READSTAT_TYPE_INT8
+  value label   => mylabl
+  storage width => 1
+  display width => 16
+  measure       => READSTAT_MEASURE_UNKNOWN
+  alignment     => READSTAT_ALIGNMENT_RIGHT
 ```
 
 For additional details, please see the [documentation][docs-stable-url].