Animate a hydrograph in a circle

spinning_hydrograph.R

## based on this code: https://twitter.com/JustTheSpring/status/1049468485334523906
library(tidyverse)
library(lubridate)
library(gganimate)
library(tidyhydat)

stn <- "08MF005"

flow_data <- hy_daily_flows(stn, start_date = "2012-01-01", end_date = "2016-12-31") %>%
  filter(!is.na(Value)) %>%
  select(date = Date, value = Value)

title <- paste0(hy_stations(stn)$STATION_NAME, " (",
                hy_stations(stn)$STATION_NUMBER, ")")


frame_count <- (max(flow_data$date) - min(flow_data$date))/ lubridate::ddays(1)
cycle_length <- 365

animation_df <- map_df(seq_len(frame_count), ~flow_data, .id = "id") %>%
  mutate(id = as.integer(id)) %>%
  mutate(view_date = min(flow_data$date) + id - 1) %>%
  filter(date <= view_date) %>%
  mutate(days_ago = (view_date - date)/ ddays(1),
         phase_dif = (days_ago %% cycle_length) / cycle_length,
         x_pos = -sin(2*pi * phase_dif),
         nearness = cos(2*pi * phase_dif),
         year = factor(year(date)))

b <- ggplot(animation_df) +
  geom_path(aes(x_pos, value, alpha = nearness, colour = year, size = -days_ago)) +
  scale_size(range = c(0,2)) +
  transition_manual(id) +
  scale_colour_viridis_d(name = "Year") +
  labs(title = title, caption = "Data from HYDAT accessed via tidyhydat package",
       y = "Discharge (m^3/s)", x = "") +
  theme_minimal() +
  guides(size = "none", alpha = "none") +
  theme(axis.text.x = element_blank())

animate(b, fps = 25, duration = 15, width = 600, height = 600)

anim_save("circular_hydrograph.gif")