我目前正在读一个类似下面例子的文件，有没有办法指定读取文件的最新版本，即如果我将文件保存为“Abroad v1.csv”，“Abroad v2.csv”I我希望它采取最新的，在这种情况下将是2。
year <- "2015"
species <- "HOM"
root <- "Y:/Pelagic Work/FIN Data"
file <- "Abroad.csv"
ABR <- file.path(root, year, species, file)
答案 0 :(得分：1)
如果合理的话，最好确定最新的＆＃34; <select name="countryselect" id="countryselect">
<?php
$db = pg_connect('host=localhost dbname=test user=myuser password=mypass');
$query = "SELECT country FROM countries";
$result = pg_query($query);
if (!$result) {
echo "Problem with query " . $query . "<br/>";
echo pg_last_error();
exit();
}
printf ("<option value=Select>Select a Country</option>");
while($myrow = pg_fetch_assoc($result)) {
printf ("<option value=$myrow[country]>$myrow[country]</option>");
}
?>
</select>
<input type="submit" name="submit" value="SAVE">
</form>
<?php
if ($nameErr == '' && $emailErr == '' && $surnameErr == '')
{
$db = pg_connect('host=localhost dbname=test user=myuser password=mypass');
$firstname = pg_escape_string($_POST['name']);
$surname = pg_escape_string($_POST['surname']);
$emailaddress = pg_escape_string($_POST['email']);
$query = "INSERT INTO host(firstname, surname, emailaddress) VALUES('" . $firstname . "', '" . $surname . "', '" . $emailaddress . "')";
$result = pg_query($db, $query);
if (!$result) {
$errormessage = pg_last_error();
echo "Error with query: " . $errormessage;
exit();
}
//printf ("These values were inserted into the database - %s %s %s", $firstname, $surname, $emailaddress);
pg_close();
}
?>
</body>
</html>
输出（this post中的数据的文件版本，也是zx8754建议的，这是一个很好的答案。）
如果必须按文件名进行，请务必小心并了解操作系统如何对字符进行排序。举个例子，举个例子。
file.info如您所见，files <- paste0("somepath/directory/filename v", 1:10, ".csv")
basenames <- basename(files)
sort(basenames)
[1] "filename v1.csv" "filename v10.csv" "filename v2.csv" "filename v3.csv" "filename v4.csv"
[6] "filename v5.csv" "filename v6.csv" "filename v7.csv" "filename v8.csv" "filename v9.csv"
tail（basenames，1）`。相反，您需要删除除指定版本顺序的所有字符，转换为正确的格式，然后排序。以下是您使用整数版本执行此操作的示例。
filename v10.csv' appears in the second position and would not be picked up by simple methods such at