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slf-documentation

Source: vignettes/slf-documentation.Rmd
slf-documentation.Rmd

SLFhelper

SLFhelper contains some easy to use functions designed to make working with the Source Linkage Files (SLFs) as efficient as possible.

Filter functions:

  • year returns financial year of interest. You can also select multiple years using c("1718", "1819", "1920")
  • recid returns recids of interest. Selecting this is beneficial for specific analysis.
  • partnerships returns partnerships of interest. Selecting certain partnerships will reduce the SLFs size.
  • col_select returns columns of interest. This is the best way to reduce the SLFs size.

Data snippets:

  • ep_file_vars returns a list of all variables in the episode files.
  • indiv_file_vars returns a list of all variables in the individual files.
  • partnerships returns a list of partnership names (HSCP_2018 codes)
  • recid returns a list of all recids available in the SLFs.
  • ep_file_bedday_vars returns a list of all bedday related variables in the SLFs.
  • ep_file_cost_vars returns a list of all cost related variables in the SLFs.

Anon CHI

  • Use the function get_chi() to easily switch anon_chi to chi.
  • Use the function get_anon_chi() to easily switch chi to anon_chi.

Memory usage in SLFS

While working with the Source Linkage Files (SLFs), it is recommended to use the features of the SLFhelper package to maximase the memory usage in posit, see PHS Data Science Knowledge Base for further guidance on memory usage in posit workbench.

Reading a full SLF file can be time consuming and take up resources on posit workbench. In the episode file there are 263 variables and around 12 million rows compared to the individual file where there are 205 variables and around 6 million rows in each file. This can be reduced by using available selections in SLFhelper to help reduce the size of the SLFs for analysis and to free up resources in posit workbench.

The tables below show the memory usage of each full size SLF.

Episode File

Year Memory Usage (GiB)
1718 22
1819 22
1920 22
2021 19
2122 21
2223 21
2324 18

Individual File

Year Memory Usage (GiB)
1718 6.8
1819 6.8
1920 7.0
2021 7.0
2122 7.0
2223 7.1
2324 5.1

If one can use selection features in SLFhelper, the session memory requirement can be reduced. There are 263 columns for a year episode file of size around 20 GiB. Hence, on average, a column with all rows takes around 0.1 GiB, which can give a rough estimate on the session memory one needs. Taking Year 1920 as a demonstration, the following tables present various sizes of extracts from the SLF files, from 5 columns to all columns, along with the amount of memory required to work with the data one reads in. Keep in mind that tables below are just recommendations, and that memory usage depends on how one handles data and optimises data pipeline.

Episode File

Column Number Memory usage (GiB) Session Memory Recommendation
5 0.5 4 GiB (4096 MiB)
10 1.4 between 4 GiB (4096 MiB) and 8 GiB (8192 MiB)
50 5.1 between 8 GiB (8192 MiB) and 16 GiB (16384 MiB)
150 13 between 20 GiB (20480 MiB) and 38 GiB (38912 MiB)
251 22 between 32 GiB (32768 MiB) and 64 GiB (65536 MiB)

Individual File

Column Number Memory usage (GiB) Session Memory Recommendation
5 0.7 4 GiB (4096 MiB)
10 0.8 4 GiB (4096 MiB)
50 2.2 between 4 GiB (4096 MiB) and 8 GiB (8192 MiB)
150 5.5 between 8 GiB (8192 MiB) and 16 GiB (16384 MiB)
193 7.0 between 11 GiB (11264 MiB) and 21 GiB (21504 MiB)