<!--
%\VignetteEngine{knitr::knitr}
%\VignetteIndexEntry{Sea ice vignette}
%\VignetteEncoding{UTF-8}
-->

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

Sea ice vignette
======

Get sea ice data at [ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/shapefiles](ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/shapefiles).

********************

### Install `rnoaa`

Install and load `rnoaa` into the R session.

If you're on Windows, you may have to install Rtools. Run `devtools::has_devel()`. If you get a `TRUE`, you're okay. If not, [install Rtools](https://cran.r-project.org/bin/windows/Rtools/).

```{r install, eval=FALSE}
install.packages("devtools")
devtools::install_github("ropensci/rnoaa")
```

```{r load}
library('rnoaa')
library('plyr')
```

### Look at data.frame's for a series of years for Feb, South pole

```{r}
urls <- sapply(seq(1979, 1990, 1), function(x) seaiceeurls(yr = x, mo = 'Feb', pole = 'S'))
out <- lapply(urls, seaice)
head(out[[1]])
```

### Map a single year/month/pole combo

```{r seaice1}
urls <- seaiceeurls(mo = 'Apr', pole = 'N', yr = 1990)
out <- seaice(urls)
library('ggplot2')
ggplot(out, aes(long, lat, group = group)) +
   geom_polygon(fill = "steelblue") +
   theme_ice()
```

### Map all years for April only for North pole

```{r seaice2}
urls <- seaiceeurls(mo = 'Apr', pole = 'N')[1:10]
out <- lapply(urls, seaice)
names(out) <- seq(1979, 1988, 1)
df <- ldply(out)
library('ggplot2')
ggplot(df, aes(long, lat, group = group)) +
  geom_polygon(fill = "steelblue") +
  theme_ice() +
  facet_wrap(~.id)
```
