r - 应用 rbinom 时在 data.table .SD 中应用的列特定参数
问题描述
我有一个data.table
我想添加基于一列的随机二项式列作为试验次数和基于其他列的多个概率:
require(data.table)
DT = data.table(
ID = letters[sample.int(26,10, replace = T)],
Quantity=as.integer(100*runif(10))
)
prob.vecs <- LETTERS[1:5]
DT[,(prob.vecs):=0]
set.seed(123)
DT[,(prob.vecs):=lapply(.SD, function(x){runif(.N,0,0.2)}), .SDcols=prob.vecs]
DT
ID Quantity A B C D E
1: b 66 0.05751550 0.191366669 0.17790786 0.192604847 0.02856000
2: l 9 0.15766103 0.090666831 0.13856068 0.180459809 0.08290927
3: u 38 0.08179538 0.135514127 0.12810136 0.138141056 0.08274487
4: d 27 0.17660348 0.114526680 0.19885396 0.159093484 0.07376909
5: o 81 0.18809346 0.020584937 0.13114116 0.004922737 0.03048895
6: f 44 0.00911130 0.179964994 0.14170609 0.095559194 0.02776121
7: d 81 0.10562110 0.049217547 0.10881320 0.151691908 0.04660682
8: t 81 0.17848381 0.008411907 0.11882840 0.043281587 0.09319249
9: x 79 0.11028700 0.065584144 0.05783195 0.063636202 0.05319453
10: j 43 0.09132295 0.190900730 0.02942273 0.046325157 0.17156554
现在我想添加五列Quantity_A
Quantity_B
Quantity_C
Quantity_D
Quantity_E
它rbinom
与第二列中的相应概率和数量一起应用。例如,Quantity_A 的第一个条目是:
set.seed(741)
sum(rbinom(66,1,0.05751550))
> 2
这个问题似乎与这篇文章非常相似:How do I pass column-specific arguments to lapply in data.table .SD? 但我似乎无法让它发挥作用。我的尝试:
DT[,(paste0("Quantity_", prob.vecs)):= mapply(function(x, Quantity){sum(rbinom(Quantity, 1 , x))}, .SD), .SDcols = prob.vecs]
rbinom(Quantity, 1, x) 中的错误:缺少参数“Quantity”,没有默认值
有任何想法吗?
解决方案
我似乎找到了一种解决方法,尽管我不太确定为什么会这样(可能与rbinom
两个参数中没有矢量化的函数有关):
首先定义一个索引:
DT[,Index:=.I]
然后按索引执行:
DT[,(paste0("Quantity_", prob.vecs)):= lapply(.SD,function(x){sum(rbinom(Quantity, 1 , x))}), .SDcols = prob.vecs, by=Index]
set.seed(789)
ID Quantity A B C D E Index Quantity_A Quantity_B Quantity_C Quantity_D Quantity_E
1: c 37 0.05751550 0.191366669 0.17790786 0.192604847 0.02856000 1 0 4 7 8 0
2: c 51 0.15766103 0.090666831 0.13856068 0.180459809 0.08290927 2 3 5 9 19 3
3: r 7 0.08179538 0.135514127 0.12810136 0.138141056 0.08274487 3 0 0 2 2 0
4: v 53 0.17660348 0.114526680 0.19885396 0.159093484 0.07376909 4 8 4 16 12 3
5: d 96 0.18809346 0.020584937 0.13114116 0.004922737 0.03048895 5 17 3 12 0 4
6: u 52 0.00911130 0.179964994 0.14170609 0.095559194 0.02776121 6 1 3 8 6 0
7: m 43 0.10562110 0.049217547 0.10881320 0.151691908 0.04660682 7 6 1 7 6 2
8: z 3 0.17848381 0.008411907 0.11882840 0.043281587 0.09319249 8 1 0 2 1 1
9: m 3 0.11028700 0.065584144 0.05783195 0.063636202 0.05319453 9 1 0 0 0 0
10: o 4 0.09132295 0.190900730 0.02942273 0.046325157 0.17156554 10 0 0 0 0 0
数字看起来对我来说很合适
如果有人找到没有索引的解决方案,仍然会受到赞赏。