---
title: "Reading Zarr V3"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{Reading Zarr V3}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

```{r, include = FALSE}
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>",
  out.width = "100%"
)
sample_dir <- tools::R_user_dir("pizzarr")
clean <- !dir.exists(sample_dir)
```

pizzarr can read Zarr stores in both V2 and V3 format. This vignette
demonstrates opening the same dataset (BCSD climate observations) stored in
each format and shows the data are identical.

## Open V2 and V3 stores

```{r}
library(pizzarr)

v2_root <- pizzarr_sample("bcsd")
v3_root <- pizzarr_sample("bcsd_v3")

v2 <- zarr_open(v2_root)
v3 <- zarr_open(v3_root)
```

## Compare group attributes

```{r}
v2_attrs <- v2$get_attrs()$to_list()
v3_attrs <- v3$get_attrs()$to_list()

identical(v2_attrs, v3_attrs)
```

## Compare arrays

```{r}
# Precipitation array
v2_pr <- v2$get_item("pr")$as.array()
v3_pr <- v3$get_item("pr")$as.array()

identical(v2_pr, v3_pr)

# Temperature array
v2_tas <- v2$get_item("tas")$as.array()
v3_tas <- v3$get_item("tas")$as.array()

identical(v2_tas, v3_tas)

# Coordinate arrays
identical(v2$get_item("latitude")$as.array(), v3$get_item("latitude")$as.array())
identical(v2$get_item("longitude")$as.array(), v3$get_item("longitude")$as.array())
identical(v2$get_item("time")$as.array(), v3$get_item("time")$as.array())
```

## Inspect an array

```{r}
v3$get_item("pr")$get_shape()

v3$get_item("pr")$get_attrs()$to_list()
```

```{r, include=FALSE}
if(clean) unlink(sample_dir, recursive = TRUE)
```