R dplyr group，ungroup，top_n和ggplot

Question

我有一個包含城市，州，年份和謀殺數量在內的多個值的對象。我用dplyr它組由城市和計算超過所有年份的總謀殺的前10個城市是這樣的：

MurderNb_reshaped2 %>% 
    select(city, state, Year, Murders) %>% 
    group_by(city) %>% 
    summarise(total = sum(Murders)) %>% 
    top_n(10, total) %>% 
    ggplot(aes(x = Year, y = Murders, fill = "red")) + 
    geom_histogram(stat = "identity") + 
    facet_wrap(~city) 

我想繪製這個只對十大城市，不是'x =一年沒有找到，因爲它已按城市分組。任何人都可以解釋我怎麼能做到這一點？

編輯：這個原始源數據https://interactive.guim.co.uk/2017/feb/09/gva-data/UCR-1985-2015.csv 這裏是我的代碼：

Deaths <- read.csv("UCR-1985-2015.csv", stringsAsFactors = F) 
MurderRate <- Deaths[, -c(5:35)] 
MurderNb <- Deaths[, -c(36:66)] 
colnames(MurderNb) <- gsub("X", "", colnames(MurderNb)) 
colnames(MurderNb) <- gsub("_raw_murder_num", "", colnames(MurderNb)) 

MurderNb_reshaped <- melt(MurderNb, id = c("city", "Agency", "state", "state_short")) 
colnames(MurderNb_reshaped) <- c("city", "Agency", "state", "state_short", "Year", "Murders") 


MurderNb_reshaped2 <- MurderNb_reshaped 

MurderNb_reshaped2 %>% 
    select(city, state, Year, Murders) %>% 
    group_by(city) %>% 
    summarise(total = sum(Murders)) %>% 
    top_n(10, total) %>% 
    ggplot(aes(x = Year, y = Murders, fill = "red")) + 
    geom_bar(stat = "identity") + 
    facet_wrap(~city) 

Answer 1

好有一對夫婦小問題。這應該是訣竅：

#this gives you the top cities 
topCities <- MurderNb_reshaped2 %>% 
    select(city, state, Year, Murders) %>% 
    group_by(city) %>% 
    summarise(total = sum(Murders)) %>% 
    top_n(10, total) 

#you then need to filter your original data to be only the data for the top cities 
MurderNb_reshaped2 <- filter(MurderNb_reshaped2, city %in% topCities$city) 

ggplot(data = MurderNb_reshaped2, aes(x = Year, y = Murders, fill = "red")) + 
geom_bar(stat = "identity") + 
facet_wrap(~city)