逆向工程累积到每日数据？

Question

我有一个数据框，其中包含日期数据和累计计数。我正在尝试对 cumsum 进行 反转以获取每日计数但还获取每组的计数。我正在尝试从数据框 A 转到数据框 B。我正在使用 R 和 tidyr.

这是代码：

df <- data.frame(cum_count = c(5, 14, 50, 5, 14, 50), state = c("Alabama", "Alabama", "Alabama", "NY", "NY", "NY"), Year = c(2012:2014, 2012:2014))

Dataframe A cum_count state Year 1 5 Alabama 2012 2 14 Alabama 2013 3 50 Alabama 2014 4 5 NY 2012 5 14 NY 2013 6 50 NY 2014

Dataframe B cum_count state Year 1 5 Alabama 2012 2 9 Alabama 2013 3 36 Alabama 2014 4 5 NY 2012 5 9 NY 2013 6 36 NY 2014

我试过使用 diff 函数:

df <- df %>%group_by(state)%>% mutate(daily_count = diff(cum_count))

但是我明白了

Error: Column daily_count must be length 3 (the number of rows) or one, not 2

告诉我你的想法。

谢谢！

Answer 1

也许你可以试试diff，例如

df <- df %>%group_by(state)%>%
  mutate(daily_count = c(cum_count[1],diff(cum_count)))

这样

> df
# A tibble: 6 x 4
# Groups:   state [2]
  cum_count state    Year daily_count
      <dbl> <chr>   <int>       <dbl>
1         5 Alabama  2012           5
2        14 Alabama  2013           9
3        50 Alabama  2014          36
4         5 NY       2012           5
5        14 NY       2013           9
6        50 NY       2014          36

这是一个基本的 R 选项，来自 ave

df <- within(df,daily_count <- ave(cum_count,state,FUN = function(x) c(x[1],diff(x))))

这样

> df
  cum_count   state Year daily_count
1         5 Alabama 2012           5
2        14 Alabama 2013           9
3        50 Alabama 2014          36
4         5      NY 2012           5
5        14      NY 2013           9
6        50      NY 2014          36

逆向工程累积到每日数据？

Reverse engineering cumulative to daily data?

diff

r

cumulative-sum

cumsum