---
title: "Seasonal Plots"
author: "Eric A. Suess"
date: "2/1/2021"
output: html_document
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```

Today we are going to take a look at a number of the time series datasets, tibbles, that are used in the [fpp3](https://otexts.com/fpp3/) book that show seasonal patterns.

A seasonal pattern is one that is exhibited over and over again at regular intervals.

```{r}
library(fpp3)
```

The book the author used the following code to create the *a10* tsibble.  

Most poeple consider the code here to be "sort of bad" code.  Why?  

Answer: The assignment to a new object in R is usually done at the start of a pipeline of code not at the end.  It is easy to missing the assignment at the end.

```{r}
PBS %>%
  filter(ATC2 == "A10") %>%
  select(Month, Concession, Type, Cost) %>%
  summarise(TotalC = sum(Cost)) %>%
  mutate(Cost = TotalC / 1e6) -> a10
```

Beware of the is in the book.  It may be hard to find code your are looking for because of this.  Better practice.

```{r}
a10 <- PBS %>%
  filter(ATC2 == "A10") %>%
  select(Month, Concession, Type, Cost) %>%
  summarise(TotalC = sum(Cost)) %>%
  mutate(Cost = TotalC / 1e6)    # 1e6 = 1000000
a10
```

```{r}
a10 %>% autoplot()
```

```{r}
write.csv(a10, "a10.csv")
```


```{r}
a10 %>% gg_season()  # plots first column
```

```{r}
a10 %>%
  gg_season(Cost, labels = "both") +
  labs(y = "$ million",
       title = "Seasonal plot: antidiabetic drug sales")
```

```{r}
a10 %>% gg_subseries()  # plots first column
```

```{r}
a10 %>%
  gg_subseries(Cost) +
  labs(y = "$ million",
       title = "Seasonal subseries plot: antidiabetic drug sales")
```

Notice that there is an upward trend in the data.  So the year is an important predictor of the TotalC.

Also notice the effect of the tend on the ACF.

```{r}
a10 %>% gg_tsdisplay(TotalC)
```

# Tourism

Filter the data to only look at trips where the purpose was a Holiday.

```{r}
holidays <- tourism %>%
  filter(Purpose == "Holiday") %>%
  group_by(State) %>%
  summarise(Trips = sum(Trips))

holidays
```

```{r}
holidays %>% autoplot(Trips) +
  labs(y = "thousands of trips",
       title = "Australian domestic holiday nights")
```

Compare two of the time series.

Victory is very well behaved Quarterly data.

```{r}
holidays %>% filter(State == "Victoria") %>% 
  gg_tsdisplay()
```

```{r}
holidays %>% filter(State == "Victoria") %>% write.csv("victoria.csv")

holidays %>% filter(State == "Victoria") %>% ACF()

holidays %>% filter(State == "Victoria") %>% ACF() %>% autoplot()
```


ACT is not so well behaved.

```{r}
holidays %>% filter(State == "ACT") %>% 
  gg_tsdisplay()
```

# Scatterplots

Now, summing over all of the different Purposes within the States.

```{r}
visitors <- tourism %>%
  group_by(State) %>%
  summarise(Trips = sum(Trips))

visitors 
```

Consider the cross-correlation between the different time series from different States.

```{r}
visitors %>%
  ggplot(aes(x = Quarter, y = Trips)) +
  geom_line() +
  facet_grid(vars(State), scales = "free_y") +
  labs(y = "Number of visitor nights each quarter (millions)")
```

The ggpairs() function assumes the different time series are down separate columns.  Note that is changes a tidy tsibble into a non-tidy tsibble.

```{r, warning=FALSE}
visitors %>%
  pivot_wider(values_from=Trips, names_from=State) %>%
  GGally::ggpairs(columns = 2:9)
```

Now consider the autocorrelation with since time series.

Can you see the autocorrelation every 4 Quarters in the Victoria time series?

```{r}
visitors %>%
  pivot_wider(values_from=Trips, names_from=State) %>% 
  select("Victoria") %>% 
  gg_lag(geom = "point")
```

```{r}
visitors %>%
  pivot_wider(values_from=Trips, names_from=State) %>% 
  select("Victoria") %>% 
  ACF() %>% 
  autoplot()
```

Can you see that there is not so clear of a seasonal pattern in the ACT time series.


```{r}
visitors %>%
  pivot_wider(values_from=Trips, names_from=State) %>% 
  select("ACT") %>% 
  gg_lag(geom = "point")
```

```{r}
visitors %>%
  pivot_wider(values_from=Trips, names_from=State) %>% 
  select("ACT") %>% 
  ACF() %>% 
  autoplot()
```