R根据条件计算值的总和

Question

这是一个数据框：

ID<-c(rep("A",3),rep("B",2), rep("C",3),rep("D",5))
cell<-c("a1","a2","a3","a1","a2","a1","a2", "a3","a1","a2","a1","a2","a3")
value<-c(2,5,3,4,5,6,9,8,7,2,5,2,4)
df<-as.data.frame(cbind(ID, cell, value))

我想计算每个ID到单元格a2（含）的所有值的总和。必须考虑单元格和ID的顺序。如果在计算总和后没有任何单元格“ a2”，则不应考虑此行。

因此，我想获得此表：

您能帮我编写这种情况吗？ 提前致谢。 最好的问候，Inna

Answer 1

假设文件已经按单元正确排序

library( tidyverse )
df %>%
  group_by( ID ) %>%
  mutate( value = cumsum( value ) ) %>%
  filter( cell == "a2" )


# # A tibble: 5 x 3
# # Groups:   ID [4]
# ID    cell  value
#   <chr> <chr> <dbl>
# 1 A     a2        7
# 2 B     a2        9
# 3 C     a2       15
# 4 D     a2        9
# 5 D     a2       16

Answer 2

我们可以将"a2"的每次出现都视为不同的组：

library(dplyr)

df %>%
  #Create a group column with every value of cell == 'a2' as different group
  group_by(ID, grp = cumsum(lag(cell == 'a2', default = TRUE))) %>%
  #Remove those groups that do not have 'a2' in them
  filter(any(cell == 'a2')) %>%
  #Sum till 'a2' value
  summarise(value =  sum(value[seq_len(match('a2', cell))]), 
            cell = last(cell)) %>%
  select(-grp)

#   ID    value cell 
#  <chr> <dbl> <chr>
#1 A         7 a2   
#2 B         9 a2   
#3 C        15 a2   
#4 D         9 a2   
#5 D         7 a2   

Answer 3

使用ave的简洁解决方案。

r <- transform(df, value=ave(value, ID, FUN=cumsum))[df$cell == "a2", ]
r
#    ID cell value
# 2   A   a2     7
# 5   B   a2     9
# 7   C   a2    15
# 10  D   a2     9
# 12  D   a2    16

Answer 4

带有data.table

的选项

library(data.table)
setDT(df)[, value := cumsum(value) , ID][cell == 'a2']

-输出

#    ID cell value
#1:  A   a2     7
#2:  B   a2     9
#3:  C   a2    15
#4:  D   a2     9
#5:  D   a2    16