在ggmap上添加輪廓

Question

首先，這是我的數據集。

Lon  Lat CPUE Temperature 
120.93 27 0.00 24.3 
121.18 27 0.62 24.2 
121.43 27 3.76 24.9 
121.6 27.25 0.87 25 
121.35 27.25 1.63 24.2 
121.1 27.25 2.66 24.8 
121.25 27.5 7.37 24.9 
121.5 27.5 6.26 25.2 
121.75 27.5 12.02 19.4 
121.95 27.75 30.40 18.5 
121.7 27.75 93.81 23.1 
121.65 28 282.83 27.1 
121.9 28 10.43 22.3 
122.15 28 36.11 18.2 
122.4 28.25 170.05 17.9 
122.15 28.25 1170.97 18.8 
122.3 28.5 0.00 18.4 
122.55 28.5 149.99 17.6 
122.8 28.75 118.27 18.5 
122.55 28.75 1838.31 17.6 
122.25 29 1218.93 21.2 
122.5 29 1245.63 18.7 
122.75 29 235.07 17.9 123 29 33.01 19.1 

這是我ggmap與CPUE數據點：

我不知道如果我能在這個ggmap添加溫線。

Answer 1

這裏的一個方法中，服用參考從this answer，因爲在數據幀的數據點不足以產生輪廓數據：

# generate regular grid since geom_contour doesn't work on this dataset 
temp <- akima::interp(df$Lon, df$Lat, df$Temperature) 
df.expanded <- expand.grid(x = temp$x, y = temp$y) 
df.expanded$z <- as.vector(temp$z) 
df.expanded <- na.omit(df.expanded) 
rm(temp) 

library(ggplot2) 

# plot contour using stat_contour() on expanded data frame 
ggmap(background) + 
    stat_contour(data = df.expanded, binwidth = 1, 
       aes(x=x,y=y,z=z)) + 
    geom_point(data = df, alpha = 0.5, 
      aes(x = Lon, y = Lat, size = CPUE)) 

數據：

df <- read.table(header = T, text = "Lon  Lat CPUE Temperature 
120.93 27 0.00 24.3 
       121.18 27 0.62 24.2 
       121.43 27 3.76 24.9 
       121.6 27.25 0.87 25 
       121.35 27.25 1.63 24.2 
       121.1 27.25 2.66 24.8 
       121.25 27.5 7.37 24.9 
       121.5 27.5 6.26 25.2 
       121.75 27.5 12.02 19.4 
       121.95 27.75 30.40 18.5 
       121.7 27.75 93.81 23.1 
       121.65 28 282.83 27.1 
       121.9 28 10.43 22.3 
       122.15 28 36.11 18.2 
       122.4 28.25 170.05 17.9 
       122.15 28.25 1170.97 18.8 
       122.3 28.5 0.00 18.4 
       122.55 28.5 149.99 17.6 
       122.8 28.75 118.27 18.5 
       122.55 28.75 1838.31 17.6 
       122.25 29 1218.93 21.2 
       122.5 29 1245.63 18.7 
       122.75 29 235.07 17.9 123 29 33.01 19.1") 

背景地圖數據：

library(ggmap) 
background <- get_map(location = c(min(df$Lon), 
            min(df$Lat), 
            max(df$Lon), 
            max(df$Lat)), 
         zoom = 8)