Question

我在SQL中看到这样的数据。

<table class="detailList" border="0" cellpadding="0" cellspacing="0">
  <tbody>
    <tr>
      <td class="data2Col  first " colspan="2">
        <div>
          <span class="labelCol vfLabelColTextWrap" scope="row" style="display:inline-block; ">Name </span>

          <span class="data2Col"> <a href="/1233" onclick="openTab('1233','Erich Schulz'); return false" target="_blank">Erich Schulz</a> </span>
        </div>
      </td>
    </tr>
    <tr>
      <th class="labelCol vfLabelColTextWrap " scope="row">Title</th>
      <td class="data2Col "><span id="j_id0:j_id1:j_id3:j_id4:j_id6"></span></td>
    </tr>
    <tr>
      <th class="labelCol vfLabelColTextWrap " scope="row">Phone</th>
      <td class="data2Col "><span id="j_id0:j_id1:j_id3:j_id4:j_id7">(555) 555-5555</span></td>
    </tr>
    <tr>
      <th class="labelCol vfLabelColTextWrap  last " scope="row">Email</th>
      <td class="data2Col  last "><span id="j_id0:j_id1:j_id3:j_id4:j_id8"><a href="mailto:test@example.com">test@example.com</a></span></td>
    </tr>
  </tbody>
</table>

尝试在R中使用以下代码来获取我想要的表：

    date_at    price
1 2016-03-02 631USD/1M
2 2016-03-02 741USD/1M
3 2016-03-02 702USD/1M
4 2016-03-02 685USD/1M
5 2016-03-02 738USD/1M
6 2016-03-02 741USD/1M

即，我试图将SQL tbl变为跟随，然后选择变量：

df <- tbl(db,"table") %>%
  mutate(newprice = as.numeric(substr(price,1,regexpr("USD",price)-1))) %>%
  select(date, newprice) %>%
  head()

但是，我无法使用上述代码创建newprice列。得到此错误：

    date_at    price    newprice
1 2016-03-02 631USD/1M  631 
2 2016-03-02 741USD/1M  741
3 2016-03-02 702USD/1M  702
4 2016-03-02 685USD/1M  685
5 2016-03-02 738USD/1M  738
6 2016-03-02 741USD/1M  741

我发现mutate只能处理应用于变量的一个函数。我应该做什么其他功能

Answer 1

这可以帮到你：

df<-data.frame(date_at=c("2016-03-02","2016-03-02","2016-03-02","2016-03-02",
                         "2016-03-02","2016-03-02"),
               price=c("631USD/1M","741USD/1M","702USD/1M","685USD/1M",
                        "738USD/1M","741USD/1M"))

df%>%
        tbl_df%>%
        mutate(newprice=as.numeric(substr(price,1,regexpr("USD",price)-1)),
               date_at=as.Date(date_at))%>%
        select(date_at,newprice)%>%
        head()     

Source: local data frame [6 x 2]

     date_at newprice
      (date)    (dbl)
1 2016-03-02      631
2 2016-03-02      741
3 2016-03-02      702
4 2016-03-02      685
5 2016-03-02      738
6 2016-03-02      741

dplyr包 - 使用mutate将两个或多个函数应用于tbl

1 个答案: