r数据表按列的第二列列表划分列

Question

我有一个脚本生成一个数据表,其中包含一些我希望除以其他列的列,并将结果存储在新列中.这是一个例子.

library(data.table)
dt <- data.table(V1 = c( 5.553465,  4.989168,  2.563682,  6.987971, 19.220936),
                 V2 = c(4.248335, 19.768138,  3.840026, 17.411003, 17.939368),
                 V3 = c(9.683953, 15.344424, 11.729091,  7.534210,  5.404000),
                 V4 = c(5.949093,  4.553023,  9.765656, 11.211069,  4.085964),
                 V5 = c(11.814671,  5.460138,  2.492230,  1.48792,  8.164280))

list1 <- list(c("V1", "V2", "V3"))
list2 <- list(c("V2", "V4", "V5"))
listRatio <- list(c("rat1","rat2","rat3"))

我尝试了各种方法来将list1元素中的值除以list2元素中的值,但未成功.两个在下面; 既不起作用.

dt[, (listRatio) := list1/list2]
dt[, c("rat1","rat2","rat3") := mapply(dt, function(x,y) x / y, x = c(V1, V2, V3),  y = c(V2, V4, V5))]

Answer 1

我们需要通过使用转换为listto ,然后在with中获取每个向量的值,使用除()每个值的相应列并将其分配给vector().vector[[listmgetMap/listlistRatio[[1]]

dt[, (listRatio[[1]]) := Map(`/`, mget(list1[[1]]), mget(list2[[1]]))]
dt
#          V1        V2        V3        V4        V5      rat1      rat2      rat3
#1:  5.553465  4.248335  9.683953  5.949093 11.814671 1.3072098 0.7141147 0.8196549
#2:  4.989168 19.768138 15.344424  4.553023  5.460138 0.2523843 4.3417611 2.8102630
#3:  2.563682  3.840026 11.729091  9.765656  2.492230 0.6676210 0.3932174 4.7062635
#4:  6.987971 17.411003  7.534210 11.211069  1.487920 0.4013537 1.5530190 5.0635854
#5: 19.220936 17.939368  5.404000  4.085964  8.164280 1.0714389 4.3904861 0.6619077

注意:正如评论中提到的@Frank,最好创建vector变量名称而不是a list.