Return date range by group

问题

I want to group by color and calculate the date range for that color. I have tried group_by(), summarize() and aggregate().

#Data:
df1 <- as.Date(c('Jul 1', 'Jun 26', 'July 5', 'July 15'), format = '%B %d')
df2 <- c("red", "blue", "red", "blue")

df1 <- data.frame(df1,df2)

What I'm trying to get:

#  Group.1   x
[1]   4     red
[2]   19    blue

I have been trying this:

df <- aggregate(df1[,1], list(df1[,2]), as.numeric(max(df1[,1]) - min(df1[,1]), units="days"))

I have tested as.numeric(max(df1[,1]) - min(df1[,1]), units="days") and it returns the value that I'm looking for, I just can't figure out how to return that value for each color.

My Error Message is below, but I think realistically, I'm just going about this the wrong way.

 Error in match.fun(FUN) : 
      'as.numeric(max(df1$date) - min(df1$date), units = "days")' is not a function, character or symbol

after reading through aggregate() document I tried to use the formula = for the last argument and returned this error:

Error in match.fun(FUN) : argument "FUN" is missing, with no default

回答1:

With dplyr:

 df1 %>% 
   group_by(df2) %>% 
   summarise(Range=max(df1) - min(df1))
# A tibble: 2 x 2
  df2   Range  
  <fct> <drtn> 
1 blue  19 days
2 red    4 days

回答2:

Using aggregate

aggregate(df1~ df2, df1, function(x) diff(range(x)))

Note that the column names of 'df1' are 'df1' and 'df2' and it creates some confusion. Instead, it may be better to create the data ass

df1 <- data.frame(x = df1, Group = df2)

and then with the formula method,

aggregate(x~ Group, df1, diff)

回答3:

require(dplyr)

df001 <- as.Date(c('Jul 1', 'Jun 26', 'July 5', 'July 15'), format = '%B %d')
df002 <- c("red", "blue", "red", "blue")

df003 <- data.frame(df001,df002)


df003 %>%  rename(dates = df001, colors = df002) %>% 
  group_by(colors) %>% 
  summarise(min_date = min(dates), max_date = max(dates)) %>%  
  mutate(range = max_date - min_date) %>%  
  select(colors, range)


# 
# # A tibble: 2 x 2
# colors range 
# <fct>  <time>
#   1 blue   19    
#   2 red    4

来源：https://stackoverflow.com/questions/57113810/return-date-range-by-group

标签

date

aggregate