如何使用变量查找在 R 中创建新列？ R编程

Question

我有一个数据 table 看起来像：

    Cause of Death                Ethnicity                 Count
1: ACCIDENTS EXCEPT DRUG POISONING ASIAN & PACIFIC ISLANDER  1368
2: ACCIDENTS EXCEPT DRUG POISONING                 HISPANIC  3387
3: ACCIDENTS EXCEPT DRUG POISONING       NON-HISPANIC BLACK  3240
4: ACCIDENTS EXCEPT DRUG POISONING       NON-HISPANIC WHITE  6825
5:              ALZHEIMERS DISEASE ASIAN & PACIFIC ISLANDER   285
---

我想创建一个新列，该列仅显示因特定死因而死亡的不同种族人口的百分比。像这样：

   Cause of Death                Ethnicity                  Count  PercentofDeath
1: ACCIDENTS EXCEPT DRUG POISONING ASIAN & PACIFIC ISLANDER  1368     0.09230769
2: ACCIDENTS EXCEPT DRUG POISONING                 HISPANIC  3387     0.22854251
3: ACCIDENTS EXCEPT DRUG POISONING       NON-HISPANIC BLACK  3240     0.21862348
4: ACCIDENTS EXCEPT DRUG POISONING       NON-HISPANIC WHITE  6825     0.46052632
5:              ALZHEIMERS DISEASE ASIAN & PACIFIC ISLANDER   285     0.04049446
---

这是我的代码，非常难看：

   library(data.table)
   #load library, change to data table
   COD.dt <- as.data.table(COD)


   #function for adding the percent column
   lala  <- function(x){ 

   #see if I have initialized data.table I'm going to append to


      if(exists("started")){
        p <- COD.dt[x ==`Cause of Death`]
        blah <- COD.dt[x ==`Cause of Death`]$Count/sum(COD.dt[x ==`Cause of Death`]$Count)
        p$PercentofDeath <- blah
        started <<- rbind(started,p)
      }

       #initialize data table
        else{
            l <- COD.dt[x ==`Cause of Death`]
            blah <- COD.dt[x ==`Cause of Death`]$Count/sum(COD.dt[x ==`Cause of Death`]$Count)
            l$PercentofDeath <- (blah)
            started <<- l  
        }

 #if finished return
if(x == unique(COD.dt$`Cause of Death`)[length(unique(COD.dt$`Cause of Death`))]){
  return(started)
 }
 }

 #run function
 h <- sapply(unique(COD.dt$`Cause of Death`), lala)
  #remove from environment
 rm(started)
 #h is actually ends up being a list, the last object happen to be the one I want so I take that one
 finalTable <- h$`VIRAL HEPATITIS`

所以，如您所见。这段代码相当难看，而且不适应table。我希望从一些指导中了解如何让它变得更好。也许使用 dpylr 或其他一些功能？

最佳

Answer 1

纯数据-table 解决方案也很简单，但这里是 dplyr:

 library(dplyr)

COD.dt %>% group_by(`Cause of Death`) %>%
    mutate(PercentofDeath = Count / sum(Count))

您可以将其转换为一个函数，但这是一个非常小的基本操作，大多数人不会费心。

Answer 2

我刚找到更好的方法：

 library(data.table)
 #load library, change to data table
 COD.dt <- as.data.table(COD)

 #make column of disease total counts
 COD.dt[,disease:=sum(Count), by = list(`Cause of Death`)] 

 #use that column to make percents
 COD.dt[,percent:=Count/disease, by = list(`Cause of Death`)]

如何使用变量查找在 R 中创建新列？ R编程

How do I create a new column in R with variable look up? R programming

variables

r

col

data.table