Question

如果EA $阶段的值为1，则新向量OCC中的等效位置必须为90.到目前为止，我有这个：

head(EA$phase)
[1] 1 1 1 1 2 2

OCC <- vector(mode = "list", length = 580) #Pre-allocate OCC
for(i in 1:length(EA$phase)) # For each element in EA$phase
{
  if (EA$phase[i]=="1"){OCC[i]=90} #If the value of EA$phase[1] is 1 then OCC[1]=90
  if (EA$phase[i]=="2"){OCC[i]=90}
  if (EA$phase[i]=="3"){OCC[i]=50}
  if (EA$phase[i]=="4"){OCC[i]=70}
  if (EA$phase[i]=="5"){OCC[i]=60}
  if (EA$phase[i]=="6"){OCC[i]=50}
  if (EA$phase[i]=="7"){OCC[i]=70}
  if (EA$phase[i]=="8"){OCC[i]=70}
  if (EA$phase[i]=="9"){OCC[i]=80}
  if (EA$phase[i]=="10"){OCC[i]=80}
}

但这不是某种方式。有没有办法使这更有效/更正确？一些技巧？

Answer 1

你可以不用for循环（没有预分配）：

occ <- c(90, 90, 50, 70, 60,  50, 70, 70, 80, 80)
OCC <- occ[EA$phase]

最终您希望将结果放在数据框中：

EA$OCC <- occ[EA$phase]

使用的技术是间接索引：您有一个变量（在本例中为EA$phase），其值是向量的索引（在本例中为occ）

Answer 2

尝试一下：

data.table

EA_DT <- data.table(phase = c(1,2,1,2,1,3,7,5))

lookup_DT <- data.table(V1 = c(1,2,3,4,5,6,7), V2 = c(90,90,50,70,60,50,70))
res1 <- merge(EA_DT, lookup_DT, by.x = "phase", by.y = "V1")

lookup_DT2 <- data.table(phase = c(1,2,3,4,5,6,7), OCC = c(90,90,50,70,60,50,70))
setkey(EA_DT, phase)
res2 <- merge(EA_DT, lookup_DT2)

data.frame

EA_DF <- data.frame(phase = c(1,2,1,2,1,3,7,5))

lookup_DF <- data.frame(V1 = c(1,2,3,4,5,6,7), V2 = c(90,90,50,70,60,50,70))
res5 <- merge(EA_DF, lookup_DF, by.x = "phase", by.y = "V1")  

lookup_DF2 <- data.frame(phase = c(1,2,3,4,5,6,7), OCC = c(90,90,50,70,60,50,70))
res6 <- merge(EA_DF, lookup_DF2)

还可以使用dplyr::left_join()等，您只需要与查找表进行左连接。

编辑：包含匹配列名的较短版本，如@jogo所建议。

for循环和if语句r + preallocation

2 个答案:

data.table

更多data.table

data.frame