获取数据帧某一列中字符串连续出现的次数

Question

我需要找出在某个数据帧的列中一个值在另一个值之后出现的次数。

主要逻辑是根据另一列获取特定字符串的出现次数。

例如：

df<- data.frame(fruits = c("apples", "apples", "orange", "pears", "apples", "pears", "pears", "papaya", "papaya"), 
                veggies = c("beans", "carrots", "carrots", "carrots", "brinjal","carrots", "brinjal", "brinjal", "beans"),
                branches=c( "Area1", "Area1", "Area1", "Area2","Area2","Area2", "Area2", "Area3", "Area3" ))

这是我的数据框。我需要知道基于树枝列的水果或蔬菜的数量

当我使用table(df$fruits)时

输出为：

apples-3 orange-1 papaya-2  pears-3

输出通常显示所有树枝的苹果和其他水果的总数。我需要准确地得到每个分支的计数。

我所需的输出应该基于列df$Branches

for Area1
   apples-2 orange-1,
for Area2 
   pears-3 apples-1
for Area3 
   papaya-3

Answer 1

试试这个：

library(data.table)
setDT(df)[,list(count=.N),list(branches, fruits)]

#   branches fruits count
#1:    Area1 apples     2
#2:    Area1 orange     1
#3:    Area2  pears     3
#4:    Area2 apples     1
#5:    Area3 papaya     2

Answer 2

也许只需要使用ftable

> ftable(fruits ~ branches, data = df)
         fruits apples orange papaya pears
branches                                  
Area1                2      1      0     0
Area2                1      0      0     3
Area3                0      0      2     0
> ftable(veggies ~ branches, data = df)
         veggies beans brinjal carrots
branches                              
Area1                1       0       2
Area2                0       2       2
Area3                1       1       0

Answer 3

我不知道您期望的输出，但您可以使用dplyr包获取计数：

例如：

library(dplyr)
df %>% count(fruits, branches)
# OR
count(df, fruits, branches)

输出：

Source: local data frame [5 x 3]
Groups: fruits

  fruits branches n
1 apples    Area1 2
2 apples    Area2 1
3 orange    Area1 1
4 papaya    Area3 2
5  pears    Area2 3