Visualize the extent of sea ice over time. Based on 2010 script by Rasmus E. Benestad. Reference for data: Fetterer, F., K. Knowles, W. Meier, and M. Savoie. 2002, updated 2009. Sea Ice Index. Boulder, CO: National Snow and Ice Data Center. Digital media. http://nsidc.org/data/g02135.html

SeaIceExtent.Rmd

---
title: "Sea Ice"
output:
  html_document: default
  html_notebook: default
---

First load up any relevant packages.
This script uses the `pacman` package to make sure any required packages are ready to go -- it's a nice tool.

```{r}
if(!require(pacman)) install.packages('pacman')
pacman::p_load(jpeg, tidyverse, readr, lubridate, ggplot2, ggthemes)
```

Next set up the raw files

```{r}
ftp1 <- "ftp://sidads.colorado.edu/pub/DATASETS/NOAA/G02135/north/daily/data/N_seaice_extent_daily_v2.1.csv"
image.name <- "http://www.realclimate.org/images//sea-ice-Hudson-Bay-Dec12-2009.jpg"
```

We're ready to read in the raw data

```{r}
nisdc <- read_csv(ftp1, skip=2, col_names = c('year', 'month', 'day', 'extent', 'missing', 'source_data'),
                  col_types =
  cols(
    year = col_integer(),
    month = col_integer(),
    day = col_integer(),
    extent = col_double(),
    missing = col_double(),
    source_data = col_character()
  )) %>%
  select(-source_data)
```

Did we do it?

```{r}
nisdc
```

To visualize we just need to do a couple of tricks on the data -- we need the day of year of each date

```{r}
nisdc <- nisdc %>% 
  mutate(date = ymd(paste(year, month, day))) %>% 
  mutate(doy = yday(date))
```

Cool, now we're ready to go!
For simplicity I'll leave off the background image.
The image is definitely a little easier to see, though the background image on the old one was kind of cool too.

```{r, fig.width=8}
plt1 <- ggplot(nisdc, aes(x = doy, y = extent)) + 
  geom_line(data = filter(nisdc, year <= 2011), aes(group = factor(year)), color='gray') +
  geom_line(data = filter(nisdc, year > 2011), aes(color = factor(year))) +
  scale_color_brewer(palette = 'Accent', name = "Year") +
  theme_base(base_size = 10) +
  labs(x = "Day of Year", y = "Arctic Sea Ice Extent [10^6 km^2]",
       title = "Arctic Sea Ice Extent: 1978--Present",
       subtitle = "Adapted from Rasmus Benestad at RealClimate.org",
       caption = "Data from http://nsidc.org/data/g02135.html. Years 1978-2011 depicted in gray.")
plt1
```

This is nice, but it would be even cooler if it was interactive.
This is possible using the `plotly` package and their super-easy `ggplot` interface

```{r, fig.width=8}
pacman::p_load(plotly)
ggplotly(plt1)
```

This isn't quite as customized, but it's pretty cool to be able to see the raw data for each year!