如何使用data.table获取R中键的每个值的百分比? [英] How to obtain percentages per value for the keys in R using data.table?
问题描述
我有一个 data.table
如下所示:
x, y, sum(count)
1, 1, 3
1, 2, 7
1, 3, 8
2, 1, 4
2, 2, 3
2, 3, 10
依此类推。它以 x
和 y
为键,我做了一个 sum
在计数
列上。我想按x的值将其分解为百分比,这样它就变成:
And so on. It's keyed by x
and y
and I did a sum
on a count
column. I would like to break it down into percentages by the values of x so that it becomes:
x, y, percentage(counts)
1, 1, 16.7
1, 2, 38.9
1, 3, 44.4
2, 1, 23.5
2, 2, 17.6
2, 3, 58.8
因此,每个 x $的总百分比c $ c>值总计为100%。我正在使用
data.table
包进行此操作。预先感谢您的帮助。
So that the total percentage per x
value totals 100%. I am doing this using the data.table
package. Thank you in advance for your help.
推荐答案
我不太了解 data.table
解决方案已经发布,所以我会这样做(并且我会更改列的名称以不使用括号,以避免对列名称使用大量反引号(!))
I don't quite understand the data.table
solution already posted, so I would do it like this (and I would change the name of the columns to not have parentheses to avoid lots of backtick quoting(!) of column names):
dt[ , `percentage(counts)` := `sum(count)` / sum( `sum(count)` ) * 100 , by = "x" ]
# x y sum(count) percentage(counts)
#1: 1 1 3 16.66667
#2: 1 2 7 38.88889
#3: 1 3 8 44.44444
#4: 2 1 4 23.52941
#5: 2 2 3 17.64706
#6: 2 3 10 58.82353
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