---
title: "Dates"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{Dates}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

```{r, include = FALSE}
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)
```

In this example, we start with a data frame with two columns, one with full dates and one with partial dates. The goal is to consolidate these dates into one ISO 8601 formatted date column. 

```{r example1, message=FALSE}
library(sdtmval)
library(dplyr)

raw_dates <- data.frame(
  raw_full = c(
    rep(NA, 8),
    "02/05/2017",
    "02-05-2017"
  ),
  raw_partial = c(
    "UN-UNK-UNKN",
    "UN/UNK/UNKN",
    "UN UNK UNKN",
    "UN-UNK-2017",
    "UN-Feb-2017",
    "05-FEB-2017",
    "05-UNK-2017",
    "05-Feb-UNKN",
    rep(NA, 2)
  )
)
knitr::kable(raw_dates)
```

First, we will re-arrange the partial dates into the same format as the full dates using `reshape_pdates()`. That will let us combine the full and partial dates into one column with a MM/DD/YYYY format. Then, using `reshape_adates()`, we will convert all dates to the YYYY-MM-DD format.

```{r example2}
working_dates <- raw_dates %>%
  mutate(
    partial = reshape_pdates(raw_partial),
    all = coalesce(raw_full, partial),
    all = reshape_adates(all)
  )
knitr::kable(working_dates)
```


For situations where missing date elements should be removed, use the `trim_dates()` function.

```{r example3}
trimmed_dates <- mutate(working_dates, trimmed = trim_dates(all))
knitr::kable(trimmed_dates)
```


If imputed dates are needed, use the `impute_pdates()` function. Both start and end dates can be imputed using standard imputation rules.

```{r example4}
imputed_dates <- working_dates %>%
  mutate(
    start = impute_pdates(all, ptype = "start"),
    end = impute_pdates(all, ptype = "end")
  )
knitr::kable(imputed_dates)
```