library(XML)
library(ggmap)
library(animation)

## 网页数据抓取和清理
Url <-"http://data.earthquake.cn/datashare/globeEarthquake_csn.html"
Data <- readHTMLTable(Url, stringsAsFactors = FALSE)
Data <- Data[[6]]
D <- Data[c(1,3,4,6)]

D$震级 <- as.numeric(gsub("[a-zA-Z]", "", D$震级))
D[2:4] <- sapply(D[2:4], as.numeric)
D$发震日期 <- as.Date(D$发震日期,  "%Y-%m-%d")

names(D) <- c("Date", "Lat", "Lon", "Level")

D1 <- D[D$Date < Sys.Date()-1,]

## 画图
### 因为 Google map api 不能使用，只好手动加载背景图。

### 中国的经纬度信息
China <- c(left = 73, bottom = 17, right = 135, top = 50)
Map <- get_stamenmap(China, zoom = 6, maptype = "toner-lite")

Day_Plot <- function(x){
  D2 <- subset(D1, Date == x)
  ggmap(Map, extent = "device") +
    geom_point(data = D2, aes(x = Lon, y = Lat), color = "red", size = D2$Level, alpha = 0.4) +
    labs(title = as.Date(x, origin = "1970-01-01"))
}

Time <- sort(unique(D1$Date))
saveGIF(for( i in Time) print(Day_Plot(i)))