从查找表创建一个新的变量 [英] Creating a new variable from a lookup table

问题描述

我在我的数据集中有以下列：

I have the following columns in my data set:

presult     aresult
  I         single
  I         double
  I         triple
  I         home run
  SS        strikeout

我要添加一个第三列依赖，这取决于列的结果值。

I would like to add a third column "bases" that is dependent upon the value of the result in column aresult.

例如，我希望基数为1单，2为双，3为三重，4为一个主场，0为一个出发。

For example, I would like bases to be 1 for a single, 2 for a double, 3 for a triple, 4 for a home run, and 0 for a strikeout.

通常我会创建一个新的变量，如下所示： / p>

Usually I would create the new variable like this:

dataset$base<-ifelse(dataset$aresult=="single", 1, 0)

问题是，我不知道如何编写新的变量而不将所有其他变量设置为零。

The problem is that I don't know how to code the new variable in without setting all other variables to zero.

推荐答案

定义查找表

lookup= data.frame( 
        base=c(0,1,2,3,4), 
        aresult=c("strikeout","single","double","triple","home run"))

然后使用join从plyr

then use join from plyr

dataset = join(dataset,lookup,by='aresult')

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