## Overview

The project files include:

-   `subject-info.csv`: NHANES SEQN (id), age, and gender for all subjects 

Two folders: `xpt` and `csv`. Within each folder are 

-   15 files, each named `nhanes_1440_<varname>.ext` where `ext` = `csv.xz` in `csv` folder, and `ext` = `xpt.xz` in `xpt` folder

-   `<varname>` is one of: `actisteps`, `adeptsteps`, `oaksteps`, `scrfsteps`, `scsslsteps`, `vssteps`, `vsrevsteps`, `AC`, `log10AC`, `PAXMTSM`, `log10PAXMTSM`, `PAXPREDM`, `PAXFLGSM`, `choiwear`, `troianowear`

-   Each row in each file is one day for one participant. Each file contains the following columns: 

    - `SEQN`: NHANES participant ID, a character scalar

    -   `PAXDAYM`: NHANES day of physical activity measurements for the participant, integer between 1 and 9. Note: days 1 and 9 will not have complete data.

    -   `PAXDAYWM`: day of the week, integer between 1 and 7, where 1 corresponds to Sunday, 2 to Monday, ..., and 7 to Saturday.

    -   `min_x` for `x = 0001, 0002, ..., 1440`: the value of `<varname>` for minute `x`. For `actisteps`, `adeptsteps`, `oaksteps`, `scrfsteps`, `scsslsteps`, `vssteps`, `vsrevsteps`, `AC`, `log10AC`, `PAXMTSM`, `log10PAXMTSM`, the values are floats. For `PAXPREDM` they are integers, where `1` = wake wear, `2` = sleep wear, `3` = unknown wear, and `4` = nonwear. For `choiwear` and `troianowear` they are logical^[`xpt` files don't support logical data types, logical values are stored as 0/1 for the xpt files (1 = TRUE, 0 = FALSE)] (TRUE = wear, FALSE = nonwear). For `PAXFLGSM` values are logical, where TRUE corresponds to any wear flags and FALSE corresponds to no wear flags.


## **Key**

-   `actisteps` = Actilife steps

-   `oaksteps` = Oak steps

-   `scrfsteps` = stepcount random forest steps

-   `scsslsteps` = stepcount SSL steps

-    `vssteps` = Verisense steps

-   `vsrevsteps` = Verisense revised steps

-   `AC` = ActiGraph activity counts

-   `log10AC` = log10 of 1 + activity counts

-   `PAXMTSM` = MIMS (monitor independent movement summary units)

-   `log10PAXMTSM` = log10 of 1 + MIMS

-   `PAXPREDM` = wear prediction (1 = Wake wear, 2 = Sleep wear, 3 = Non wear, 4 = unknown), from [Detecting Sleep and Nonwear in 24-h Wrist Accelerometer Data from the National Health and Nutrition Examination Survey](https://pubmed.ncbi.nlm.nih.gov/36007161/)

-   `choiwear` = result of [Choi wear algorithm](https://pubmed.ncbi.nlm.nih.gov/20581716/) (TRUE if wear, FALSE if nonwear)^[Choi and Troiano algorithms were all implemented using the [`actigraph.sleepr`](https://github.com/dipetkov/actigraph.sleepr) R package.]

-   `troianowear` = result of [Troiano wear algorithm]( https://doi.org/10.1249/mss.0b013e31815a51b3) (TRUE if wear, FALSE if nonwear)

-   `PAXFLGSM` = data quality flags (`TRUE` if any flag, `FALSE` otherwise) flag description [here](https://wwwn.cdc.gov/Nchs/Data/Nhanes/Public/2011/DataFiles/PAXMIN_G.htm#PAXFLGSM)