Загружаем данные о распространении COVID-19:

#'
#' Load COVID-19 spread: infected, recovered, and fatal cases
#' Source: https://github.com/CSSEGISandData/COVID-19/tree/master/csse_covid_19_data/csse_covid_19_time_series
#'
load_covid_spread <- function() {
  require(dplyr)
  require(data.table)
  require(purrr)
  require(tidyr)

  load_time_series <- function(.case_type) {

    path_pattern <- "https://raw.githubusercontent.com/CSSEGISandData/COVID-19/master/csse_covid_19_data/csse_covid_19_time_series/time_series_covid19_%s_global.csv"

    fread(sprintf(path_pattern, .case_type)) %>% 
      rename(country = `Country/Region`) %>% 
      select(-c(`Province/State`, Lat, Long)) %>% 
      group_by(country) %>% 
      summarise_if(is.numeric, sum) %>% 
      ungroup %>% 
      gather(key = "date", value = "n", -country) %>% 
      mutate(date = mdy(date))
  }

  dt <- load_time_series("confirmed") %>% rename(confirmed_n = n) %>% 
    inner_join(
      load_time_series("recovered") %>% rename(recovered_n = n),
      by = c("country", "date")
    ) %>% 
    inner_join(
      load_time_series("deaths") %>% rename(deaths_n = n),
      by = c("country", "date")
    ) 

  stopifnot(nrow(dt) > 0)

  return(dt)
}

spread_raw <- load_covid_spread()
spread_raw %>% sample_n(10)

Загружаем данные о популяции стран:

#'
#' Load countries stats
#' Source: https://ods.ai/competitions/sberbank-covid19-forecast
#'
load_countries_stats <- function() {
  require(dplyr)
  require(magrittr)

  dt <- fread("https://raw.githubusercontent.com/codez0mb1e/covid-19/master/data/countries.csv")

  dt %<>%
    select(-c(iso_alpha2, iso_numeric, name, official_name))

  stopifnot(nrow(dt) > 0)

  return(dt)
}

countries_raw <- load_countries_stats()
countries_raw %>% sample_n(10)

Предобработка данных:

data <- spread_raw %>% 
  # add country population
  inner_join(
    countries_raw %>% transmute(ccse_name, country_iso = iso_alpha3, population) %>% filter(!is.na(country_iso)), 
    by = c("country" = "ccse_name")
  ) %>% 
  # calculate active cases
  mutate(
    active_n = confirmed_n - recovered_n - deaths_n
  ) %>% 
  # calculate cases per 1M population
  mutate_at(
    vars(ends_with("_n")),
    list("per_1M" = ~ ./population*1e6)
  )

## Calculte number of days since...
get_date_since <- function(dt, .case_type, .n) {
  dt %>% 
    group_by(country) %>% 
    filter_at(vars(.case_type), ~ . > .n) %>% 
    summarise(since_date = min(date))
}

data %<>% 
  inner_join(
    data %>% get_date_since("confirmed_n", 0) %>% rename(since_1st_confirmed_date = since_date),
    by = "country"
  ) %>% 
  inner_join(
    data %>% get_date_since("confirmed_n_per_1M", 1) %>% rename(since_1_confirmed_per_1M_date = since_date),
    by = "country"
  ) %>% 
  inner_join(
    data %>% get_date_since("deaths_n_per_1M", .1) %>% rename(since_dot1_deaths_per_1M_date = since_date),
    by = "country"
  ) %>% 
  mutate_at(
    vars(starts_with("since_")), 
    list("n_days" = ~ difftime(date, ., units = "days") %>% as.numeric)
  ) %>% 
  mutate_at(
    vars(ends_with("n_days")),
    list(~ if_else(. > 0, ., NA_real_))
  )

Настройки для графиков:

theme_set(theme_minimal())

lab_caption <- paste0(
  "Data source: Novel Coronavirus (COVID-19) Cases provided by Johns Hopkins University Center for Systems Science. \n",
  sprintf("Last updated: %s. ", format(max(data$date), '%d %B, %Y')),
  "Source code: github.com/codez0mb1e/covid-19"
) 

filter_countries <- function(dt) dt %>% filter(country_iso %in% c("KOR", "ITA", "RUS", "CHN", "USA"))

ggplot(data %>% filter_countries, aes(x = date)) +
  geom_col(aes(y = confirmed_n), alpha = .9) +

  scale_x_date(date_labels = "%d %b", date_breaks = "7 days") +

  facet_grid(country ~ .) +

  labs(x = "", y = "# of cases", 
       title = "COVID-19 Spread (over time)", 
       caption = lab_caption) +

  theme(plot.caption = element_text(size = 8))

ggplot(data %>% filter_countries, aes(x = date)) +
  geom_col(aes(y = confirmed_n), alpha = .9) +

  scale_x_date(date_labels = "%d %b", date_breaks = "7 days") +
  scale_y_log10() +

  facet_grid(country ~ .) +

  labs(x = "", y = "# of cases", 
       title = "COVID-19 Spread (over time)", 
       caption = lab_caption) +

  theme(plot.caption = element_text(size = 8))

ggplot(data  %>% filter_countries, aes(x = date)) +
  geom_col(aes(y = confirmed_n_per_1M), alpha = .9) +

  scale_x_date(date_labels = "%d %b", date_breaks = "7 days") +

  facet_grid(country ~ .) +

  labs(x = "", y = "# of cases per 1M", 
       subtitle = "Infected cases per 1 million popultation",
       title = "COVID-19 Spread (over time)", 
       caption = lab_caption) +

  theme(plot.caption = element_text(size = 8))

ggplot(data  %>% filter_countries, aes(x = date)) +
  geom_col(aes(y = confirmed_n_per_1M), alpha = .9) +

  scale_x_date(date_labels = "%d %b", date_breaks = "7 days") +
  scale_y_log10() +

  facet_grid(country ~ .) +

  labs(x = "", y = "# of cases per 1M", 
       subtitle = "Infected cases per 1 million popultation",
       title = "COVID-19 Spread (over time)", 
       caption = lab_caption) +

  theme(plot.caption = element_text(size = 8))

ggplot(
  data %>% filter_countries %>% filter(!is.na(since_1st_confirmed_date_n_days)), 
  aes(x = since_1st_confirmed_date_n_days)
  ) +

  geom_col(aes(y = confirmed_n), alpha = .9) +
  scale_y_log10() +

  facet_grid(country ~ .) +

  labs(x = "# of days since 1st infected case", y = "# of cases", 
       subtitle = "Infected cases since 1st infected case",
       title = "COVID-19 Spread", 
       caption = lab_caption) +

  theme(plot.caption = element_text(size = 8))

ggplot(
  data %>% filter_countries %>% filter(!is.na(since_1_confirmed_per_1M_date_n_days)), 
  aes(x = since_1_confirmed_per_1M_date_n_days)
  ) +

  geom_col(aes(y = confirmed_n_per_1M), alpha = .9) +

  scale_y_log10() +
  xlim(c(0, 55)) +

  facet_grid(country ~ .) +

  labs(x = "# of days since 1 infected cases per 1M", y = "# of cases per 1M", 
       title = "COVID-19 Spread", 
       subtitle = "Since 1 infected cases per 1 million popultation",
       caption = lab_caption) +

  theme(plot.caption = element_text(size = 8))

plot_data <- data %>% 
  filter_countries %>% 
  filter(!is.na(since_1_confirmed_per_1M_date_n_days)) %>% 
  mutate(
    confirmed_n_per_1M = confirmed_n_per_1M, 
    recovered_n_per_1M = -recovered_n_per_1M,
    deaths_n_per_1M = -deaths_n_per_1M
  ) %>% 
  select(
    country, since_1_confirmed_per_1M_date_n_days, ends_with("_n_per_1M")
  ) %>% 
  gather(
    key = "case_state", value = "n_per_1M", -c(country, since_1_confirmed_per_1M_date_n_days, active_n_per_1M)
  )

ggplot(plot_data, aes(x = since_1_confirmed_per_1M_date_n_days)) +

  geom_col(aes(y = n_per_1M, fill = case_state), alpha = .9) +
  geom_line(aes(y = active_n_per_1M), color = "#0080FF", size = .25) +

  scale_fill_manual(element_blank(), 
                    labels = c("confirmed_n_per_1M" = "Infected cases", "recovered_n_per_1M" = "Recovered cases", "deaths_n_per_1M" = "Fatal cases"),
                    values = c("confirmed_n_per_1M" = "grey", "recovered_n_per_1M" = "gold", "deaths_n_per_1M" = "black")) +

  xlim(c(0, 55)) +

  facet_grid(country ~ ., scales = "free") +

  labs(x = "# of days since 1 infected cases per 1M", y = "# of cases per 1M", 
       title = "COVID-19 Spread by Countries", 
       subtitle = "Active cases trend since 1 infected cases per 1 million popultation. \nBlue line - infected cases minus recovered and fatal.\nNegative values indicate recovered and fatal cases.", 
       caption = lab_caption) +

  theme(
    legend.position = "top",
    plot.caption = element_text(size = 8)
  )

forecast_cases <- function(.country, .after_date, .forecast_horizont, .fun, ...) {

  dt <- data %>% 
    # filter rows and cols
    filter(
      country == .country & 
      date < .after_date
    ) %>%
    # convert to time-series
    arrange(date) %>% 
    select(active_n_per_1M)

  dt %>%  
    ts(frequency = 7) %>% 
    # ARIMA model
    .fun(...) %>% 
    # forecast
    forecast(h = .forecast_horizont)
}

forecast_horizont <- 7
after_date <- max(data$date) + days()

countries_list <- c("Belgium", "France", "Italy", "Netherlands", "Norway", "Portugal", "Spain", "Switzerland", "US", "Russia", "China", "Korea, South")

pred <- countries_list  %>% 
  map_dfr(
    function(.x) {

      m <- forecast_cases(.x, after_date, forecast_horizont, auto.arima)

      n_days_max <- max(data[data$country == .x, ]$since_1_confirmed_per_1M_date_n_days, na.rm = T)

      tibble(
        country = rep(.x, forecast_horizont),
        since_1_confirmed_per_1M_date_n_days = seq(n_days_max + 1, n_days_max + forecast_horizont, by = 1),
        pred = m$mean %>% as.numeric %>% round %>% as.integer,
        data_type = "Forecast"
      )
    }
  )

plot_data <- data %>% 
  filter(country %in% countries_list) %>% 
  transmute(
    country, active_n_per_1M, since_1_confirmed_per_1M_date_n_days, 
    data_type = "Historical data"
  ) %>% 
  bind_rows(
    pred %>% rename(active_n_per_1M = pred)
  ) %>% 
  mutate(
    double_every_14d = (1 + 1/14)^since_1_confirmed_per_1M_date_n_days, # double every 2 weeks
    double_every_7d = (1 + 1/7)^since_1_confirmed_per_1M_date_n_days, # double every week
    double_every_3d = (1 + 1/3)^since_1_confirmed_per_1M_date_n_days, # double every 3 days
    double_every_2d = (1 + 1/2)^since_1_confirmed_per_1M_date_n_days # double every 2 days
  )

active_n_per_1M_last <- plot_data %>% 
  group_by(country) %>% 
  arrange(desc(since_1_confirmed_per_1M_date_n_days)) %>% 
  filter(row_number() == 1) %>% 
  ungroup

plot_data %<>% 
  left_join(
    active_n_per_1M_last %>% transmute(country, active_n_per_1M_last = active_n_per_1M, since_1_confirmed_per_1M_date_n_days),
    by = c("country", "since_1_confirmed_per_1M_date_n_days")
  )

ggplot(plot_data, aes(x = since_1_confirmed_per_1M_date_n_days)) +

  geom_line(aes(y = double_every_7d), linetype = "dotted", color = "red", alpha = .65) +
  geom_line(aes(y = double_every_3d), linetype = "dotted", color = "red", alpha = .75) + 
  geom_line(aes(y = double_every_2d), linetype = "dotted", color = "red", alpha = .85) + 

  geom_line(aes(y = active_n_per_1M, color = country, linetype = data_type), show.legend = T) +
  geom_text(aes(y = active_n_per_1M_last + 20, label = country, color = country), 
            hjust = 0.5, vjust = 0, check_overlap = T, show.legend = F, fontface = "bold", size = 3.6) +

  annotate(geom = "text", label = "Cases double \n every 2 days", x = 17, y = 1550, vjust = 0, size = 3.1) +
  annotate(geom = "text", label = "...every 3 days", x = 25, y = 1800, vjust = 0, size = 3.1) +
  annotate(geom = "text", label = "...every week", x = 50, y = 1500, vjust = 0, size = 3.1) +

  scale_linetype_manual(values = c("longdash", "solid")) +

  xlim(c(10, 55)) +
  ylim(c(0, max(plot_data$active_n_per_1M))) +

  labs(x = "# of days since 1 infected cases per 1M", y = "# of cases per 1M", 
       title = "COVID-19 Spread by Countries", 
       subtitle = "Active cases trend since 1 infected cases per 1 million popultation.", 
       caption = lab_caption) +

  theme(
    legend.position = "bottom",
    legend.title = element_blank(),
    plot.caption = element_text(size = 8)
  )

ggplot(data %>% filter(country %in% countries_list), aes(x = date)) +

  geom_line(aes(y = confirmed_n, color = country), show.legend = T) +

  scale_x_date(date_labels = "%d %b", date_breaks = "7 days") +

  labs(x = "", y = "# of cases", 
       title = "COVID-19 Spread by Country", 
       subtitle = "Infected cases over time",
       caption = lab_caption) +

  theme(
    legend.position = "bottom",
    legend.title = element_blank(),
    plot.caption = element_text(size = 8)
  )
![image](https://github.com/codez0mb1e/covid-19/raw/master/posts/img/с_1.png)