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我有以下 data.frame 命名countries_tools。它由 3 列组成（一个日期时间列（过去 13 个月）、一个名称列（包含国家）和一个访问列（从这些特定国家访问该页面的人））：

datetime            name           Visits
2016-07-01 00:00:00 China          5237
2016-07-01 00:00:00 Germany        1434
2016-07-01 00:00:00 United States  1530
2016-07-01 00:00:00 India          696
2016-07-01 00:00:00 Japan          569
...
2017-07-01 00:00:00 China          4484
2017-07-01 00:00:00 Germany        1593
2017-07-01 00:00:00 United States  1438
2017-07-01 00:00:00 India          1204
2017-07-01 00:00:00 Japan          538

请注意，我删除了其间的其他 11 个月。另请注意，该名称始终是相同 5 个国家/地区的列表，这与上一个分析月份（本例中为 2017 年 7 月）访问次数较多的五个国家相对应。

在此消息的末尾有一个 dput与我的数据。

为了更好地了解数月访问的数据和发展，我dcast从我的 data.frame 中做了一个：

countries_tools <- dcast(countries_tools, datetime ~ name, value.var="Visits")

但是，生成的数据框按国家名称（按字母顺序）对列进行排序：

> names(countries_tools)
[1] "datetime"      "China"         "Germany"       "India"         "Japan"         "United States"

顺序是字母顺序，而不是变量值

但是，我希望顺序是由值变量（访问）完成的，因此最佳顺序应该是：

日期时间，中国，德国，美国，印度，日本

可以做到吗（充其量是不需要额外的步骤）？使用其他功能也是可能的。

数据

dput(countries_tools)
structure(list(datetime = structure(c(1467320400, 1467320400, 
1467320400, 1467320400, 1467320400, 1469998800, 1469998800, 1469998800, 
1469998800, 1469998800, 1472677200, 1472677200, 1472677200, 1472677200, 
1472677200, 1475269200, 1475269200, 1475269200, 1475269200, 1475269200, 
1477951200, 1477951200, 1477951200, 1477951200, 1477951200, 1480543200, 
1480543200, 1480543200, 1480543200, 1480543200, 1483221600, 1483221600, 
1483221600, 1483221600, 1483221600, 1485900000, 1485900000, 1485900000, 
1485900000, 1485900000, 1488319200, 1488319200, 1488319200, 1488319200, 
1488319200, 1490994000, 1490994000, 1490994000, 1490994000, 1490994000, 
1493586000, 1493586000, 1493586000, 1493586000, 1493586000, 1496264400, 
1496264400, 1496264400, 1496264400, 1496264400, 1498856400, 1498856400, 
1498856400, 1498856400, 1498856400), class = c("POSIXct", "POSIXt"
), tzone = "Europe/Moscow"), name = c("China", "Germany", "United States", 
"India", "Japan", "China", "Germany", "United States", "India", 
"Japan", "China", "Germany", "United States", "India", "Japan", 
"China", "Germany", "United States", "India", "Japan", "China", 
"Germany", "United States", "India", "Japan", "China", "Germany", 
"United States", "India", "Japan", "China", "Germany", "United States", 
"India", "Japan", "China", "Germany", "United States", "India", 
"Japan", "China", "Germany", "United States", "India", "Japan", 
"China", "Germany", "United States", "India", "Japan", "China", 
"Germany", "United States", "India", "Japan", "China", "Germany", 
"United States", "India", "Japan", "China", "Germany", "United States", 
"India", "Japan"), Visits = c(5237, 1434, 1530, 696, 569, 4422, 
1508, 1971, 672, 461, 3993, 1521, 1901, 2027, 517, 3656, 1764, 
1716, 993, 509, 5483, 3117, 2762, 1298, 594, 5548, 2804, 2365, 
1222, 551, 3747, 3083, 1917, 999, 496, 3903, 2136, 1751, 1229, 
611, 5638, 2721, 2074, 1569, 533, 4326, 1618, 1511, 1254, 458, 
4364, 2021, 1690, 1162, 462, 4462, 1572, 1517, 1068, 574, 4484, 
1593, 1438, 1204, 538)), .Names = c("datetime", "name", "Visits"
), row.names = c(NA, -65L), class = "data.frame")
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1 回答 1

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您可以将“名称”转换为有序因子，说明您想要的级别顺序： 

countries_tools$name <- ordered(countries_tools$name, levels = unique(countries_tools$name))

现在它起作用了：

dcast(countries_tools, datetime ~ name, value.var="Visits")
于 2017-08-23T08:24:29.310 回答