如何拆分數據幀並能夠使用R

Question

中的子數據框處理問題。我有一個數據幀，假設是這樣的：

sp rd pH abund area point 
dog uniq 4.5  5 1  a 
dog uniq 4.2  5 1  a 
dog for 6.1  3 1  a 
cat uniq 7.0  8 1  a 
cat uniq 4.9  5 1  a 
cat mains 3.1  9 1  b 
cat mains 6.5  1 1  b 
cat mains 6.5  3 1  b 
dog for NA  2 2  a 
bird mac 5.0 3 2  a 
bird mac 4.1 5 2  a 
bird mac 5.1 NA 2  a 
rabb lol 5.0  8 2  b 
rabb lol 4.2  5 2  b 
rabb lol 6.0  2 2  b 
rabb lol 2.8  3 2  b 

和ID喜歡通過area和point獨特的組合在幾個dataframes拆分此數據框（1A，1B，2A，2B），並希望仍然能夠一起工作他們分開。例如，我想找出每組中的均值。我嘗試使用split函數，但問題是，每個組只有名稱，例如1.a，我不能命令R在此數據框內執行任何操作。

Thx for answers。

Answer 1

如果我理解你的問題正確，這裏是我下面嘗試：

sp <- 
c("dog","dog","dog","cat","cat","cat","cat","cat","dog","bird","bird", 
"bird","rabb","rabb","rabb","rabb") 

rd <- 
c("uniq","uniq","for","uniq","uniq","mains","mains","mains", 
"for","mac","mac","mac","lol","lol","lol","lol") 

pH <- 
c(4.5,4.2,6.1,7.0,4.9,3.1,6.5,6.5,NA,5.0,4.1,5.1,5.0,4.2,6.0,2.8) 

abund <- 
c(5,5,3,8,5,9,1,3,2,3,5,NA,8,5,2,3) 

area <- 
c(1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2) 

point <- 
c("a","a","a","a","a","b","b","b","a","a","a","a","b","b","b","b") 

df <- data.frame(sp,rd,pH,abund,area,point) 

cols <-c("area","point") 

df$group <- apply(df[,cols],1,paste,collapse="") 
df$group <- as.factor(df$group) 
str(df$group) 
sapply(split(df$abund,df$group),mean,na.rm=TRUE) 

讓我知道

1a  1b  2a  2b 
5.200000 4.333333 3.333333 4.500000 

下面是一個選擇，如果有人不希望拆分數據幀。這裏的數據框架的樣子，現在在此基礎上一步

df$group <- apply(df[,cols],1,paste,collapse="") 
df 
    sp rd pH abund area point group 
1 dog uniq 4.5  5 1  a 1a 
2 dog uniq 4.2  5 1  a 1a 
3 dog for 6.1  3 1  a 1a 
4 cat uniq 7.0  8 1  a 1a 
5 cat uniq 4.9  5 1  a 1a 
6 cat mains 3.1  9 1  b 1b 
7 cat mains 6.5  1 1  b 1b 
8 cat mains 6.5  3 1  b 1b 
9 dog for NA  2 2  a 2a 
10 bird mac 5.0  3 2  a 2a 
11 bird mac 4.1  5 2  a 2a 
12 bird mac 5.1 NA 2  a 2a 
13 rabb lol 5.0  8 2  b 2b 
14 rabb lol 4.2  5 2  b 2b 
15 rabb lol 6.0  2 2  b 2b 
16 rabb lol 2.8  3 2  b 2b 

現在如果你想按組劃分：

df1a <- df[grepl("1a",df$group),] 

df1a 

    sp rd pH abund area point group 
1 dog uniq 4.5  5 1  a 1a 
2 dog uniq 4.2  5 1  a 1a 
3 dog for 6.1  3 1  a 1a 
4 cat uniq 7.0  8 1  a 1a 
5 cat uniq 4.9  5 1  a 1a 

Answer 2

嘗試使用「GROUP_BY」。我不確定你想要的確切數據，但如果你想要每個面積和點的組合的平均pH值，你可以這樣做：

你顯然必須處理你的NA值，但是這將會通過獨特的組合組合來解決問題。

df.grp <- group_by(df, area, point) %>% 
summarize(meanpH = mean(pH))