Question

我在R上工作。我想提取向量中最后一个空格和字符串模式（“ -APPLE”）之间的所有数字。这些数字可以是可变长度的。

    <?php

    session_start();
    if(isset($_POST['login'])){
        //echo  "process login";
        $doc = new DOMDocument('1.0', 'utf-8');
        $doc->preserveWhiteSpace = false;
        $doc->formatOutput = true;
        //load XML
        $xmlPath = "users.xml";
        $doc->load($xmlPath);

        //root element
        $users = $doc->getElementsByTagName("users")[0];
        //create a new <user> element
        $user = $doc->createElement("user");
        //create the role attribute and append to <person>
        $attr = $doc->createAttribute("id");
        $attr->value =""; // yet not incrementing values
        //$attr->value = count(preceding::user) + 1;
        $user->appendChild($attr);
        //create an element <username> and get a value from textbox and post to xml file
        $username = $doc->createElement("username");
        $usernameText = $doc->createTextNode($_POST['username']); //this should be sanitized
        $username->appendChild($usernameText);
        //assign textfield value to root element in xml file
        $user->appendChild($username);
        $users->appendChild($user);
//to print multiple chatroom files from xml file
    $xml = simplexml_load_file("chatrooms.xml");
    foreach ($xml as $chatroom) 
     {
      print "<a href = ' $chatroom->chatroomname ' >" . $chatroom->chatroomname . "</a>" . '<br />';

     }

    }
    ?>

预期结果集应为向量，如c（2，25，567，NA）

Answer 1

有关使用Regex group capture in R with multiple capture-groups软件包中的str_match()的示例，请参见stringr。

在您的情况下：

> test_string = c("ABC 2-APPLE", "123 25-APPLE", "DEF GHI 567-APPLE")
> 
> library(stringr)
> x <- str_match(test_string, " ([0-9]+)-APPLE$")[,2]
> as.numeric(x)
[1]   2  25 567

Answer 2

您可以使用“ rebus”软件包，该软件包在创建所需的regex模式时非常用户友好。

killed

是否有R函数提取所有数字，然后提取特定的模式？

2 个答案: