如何在r中循环ggplot图

Question

我有一个如下所示的数据集 (A2)；

Year    Gear      Region    Landings.t
1975    Creel     Clyde     3.456
1976    Creel     Clyde     20.531
1977    Creel     Clyde     56.241
1978    Creel     Clyde     43.761
1975    Creel     Shetland  3.456
1976    Creel     Shetland  10.531
1977    Creel     Shetland  46.241
1978    Creel     Shetland  33.761

我正在使用以下代码生成折线图；

ggplot(subset(A2,Region=="Clyde"),aes(x=Year,y=Landings.t,colour=Gear,group=Gear))+
  geom_line()+
  facet_grid(Gear~.,scales='free_y')+
  ggtitle("CLYDE LANDINGS BY GEAR TIME-SERIES")+
  theme(panel.background=element_rect(fill='white',colour='black'))+
  geom_vline(xintercept=1984)

目前我正在为每个不同的区域复制代码，这使得我的脚本很长。我想知道是否有一种方法可以循环代码以遍历每个区域并为每个区域生成一个图？

我已尝试使用上一个问题Loop through a series of qplots 提供的答案，但是当我使用此代码时，它会返回“二进制运算符的非数字参数”错误。

for(Var in names(A2$Region)){
print(ggplot(A2,[,Var],aes(x=Year,y=Landings.t,colour=Gear,group=Gear))+
geom_line()+
facet_grid(Gear~.,scales='free_y')+
ggtitle("CLYDE LANDINGS BY GEAR TIME-SERIES")+
theme(panel.background=element_rect(fill='white',colour='black'))+
geom_vline(xintercept=1984)
}

Answer 1

for(Var in unique(A2$Region)){
  print(
    ggplot(
      subset(A2, Region == Var),
      aes(x = Year, y = Landings.t, colour = Gear, group = Gear)
    )+
    geom_line() +
    facet_grid(Gear ~ ., scales = 'free_y') +
    ggtitle("CLYDE LANDINGS BY GEAR TIME-SERIES") +
    theme(panel.background = element_rect(fill = 'white', colour = 'black'))+
    geom_vline(xintercept = 1984)
  )
}

或使用plyr 包

library(plyr)
dlply(A2, ~Region, function(x){
    ggplot(
      x,
      aes(x = Year, y = Landings.t, colour = Gear, group = Gear)
    )+
    geom_line() +
    facet_grid(Gear ~ ., scales = 'free_y') +
    ggtitle("CLYDE LANDINGS BY GEAR TIME-SERIES") +
    theme(panel.background = element_rect(fill = 'white', colour = 'black'))+
    geom_vline(xintercept = 1984)
})

plyr 可以轻松地将数据集拆分为多个变量。

dlply(A2, ~Region + Species, function(x){
    ggplot(
      x,
      aes(x = Year, y = Landings.t, colour = Gear, group = Gear)
    )+
    geom_line() +
    facet_grid(Gear ~ ., scales = 'free_y') +
    ggtitle("CLYDE LANDINGS BY GEAR TIME-SERIES") +
    theme(panel.background = element_rect(fill = 'white', colour = 'black'))+
    geom_vline(xintercept = 1984)
})