R - 如何使用循环根据匹配名称列表复制和更改数据框

Question

我有一个由各种物种组成的数据框，以及一个显示它们存在的列(检测列)。我想以一个数据框列表结束，每个物种一个。在每个物种新数据框中，我希望匹配的物种检测值变为“1”，同时将所有其他物种检测值保持为 0。这是一个包含两个物种的示例数据框:

structure(list(Camera.Trap.Name = c("CT-Tst-1-1", "CT-Tst-2-1", 
"CT-Tst-2-1", "CT-Tst-2-1", "CT-Tst-2-1", "CT-Tst-2-1", "CT-Tst-2-1", 
"CT-Tst-2-1", "CT-Tst-3-1", "CT-Tst-3-1", "CT-Tst-3-1", "CT-Tst-3-1", 
"CT-Tst-5-1", "CT-Tst-5-1", "CT-Tst-5-1", "CT-Tst-5-1", "CT-Tst-5-1", 
"CT-Tst-5-1", "CT-Tst-5-1", "CT-Tst-5-1", "CT-Tst-5-1", "CT-Tst-5-1", 
"CT-Tst-5-1", "CT-Tst-5-1", "CT-Tst-5-1", "CT-Tst-5-1", "CT-Tst-5-1", 
"CT-Tst-5-1", "CT-Tst-5-1", "CT-Tst-5-1", "CT-Tst-5-1", "CT-Tst-5-1", 
"CT-Tst-5-1", "CT-Tst-5-1", "CT-Tst-8-1", "CT-Tst-8-1", "CT-Tst-8-1", 
"CT-Tst-8-1", "CT-Tst-8-1", "CT-Tst-8-1", "CT-Tst-8-1", "CT-Tst-8-1", 
"CT-Tst-8-1", "CT-Tst-9-1", "CT-Tst-9-1", "CT-Tst-9-1"), Sampling.Event = c("Olney 1", 
"Olney 2", "Olney 2", "Olney 2", "Olney 2", "Olney 2", "Olney 2", 
"Olney 2", "Olney 3", "Olney 3", "Olney 3", "Olney 3", "Olney 5", 
"Olney 5", "Olney 5", "Olney 5", "Olney 5", "Olney 5", "Olney 5", 
"Olney 5", "Olney 5", "Olney 5", "Olney 5", "Olney 5", "Olney 5", 
"Olney 5", "Olney 5", "Olney 5", "Olney 5", "Olney 5", "Olney 5", 
"Olney 7", "Olney 7", "Olney 7", "Olney 7", "Olney 7", "Olney 7", 
"Olney 7", "Olney 7", "Olney 7", "Olney 7", "Olney 7", "Olney 7", 
"Olney 5", "Olney 5", "Olney 5"), Photo.Date = c("2018-03-28", 
"2018-04-20", "2018-05-02", "2018-05-07", "2018-05-09", "2018-05-10", 
"2018-05-11", "2018-05-15", "2019-11-13", "2019-11-14", "2019-11-15", 
"2019-11-16", "2020-03-24", "2020-03-25", "2020-03-26", "2020-03-31", 
"2020-04-01", "2020-04-02", "2020-04-03", "2020-04-04", "2020-04-04", 
"2020-04-05", "2020-04-06", "2020-04-06", "2020-04-07", "2020-04-07", 
"2020-04-08", "2020-04-09", "2020-04-10", "2020-04-11", "2020-04-11", 
"2020-04-23", "2020-04-24", "2020-05-02", "2020-04-28", "2020-04-29", 
"2020-04-30", "2020-05-01", "2020-05-02", "2020-05-03", "2020-05-04", 
"2020-05-05", "2020-05-06", "2020-04-01", "2020-04-05", "2020-04-06"
), Species_name = c("Vulpes vulpes", "Vulpes vulpes", "Vulpes vulpes", 
"Vulpes vulpes", "Vulpes vulpes", "Vulpes vulpes", "Vulpes vulpes", 
"Vulpes vulpes", "Vulpes vulpes", "Vulpes vulpes", "Vulpes vulpes", 
"Vulpes vulpes", "Vulpes vulpes", "Lutra lutra", "Vulpes vulpes", 
"Vulpes vulpes", "Vulpes vulpes", "Vulpes vulpes", "Vulpes vulpes", 
"Lutra lutra", "Vulpes vulpes", "Vulpes vulpes", "Lutra lutra", 
"Vulpes vulpes", "Lutra lutra", "Vulpes vulpes", "Vulpes vulpes", 
"Vulpes vulpes", "Vulpes vulpes", "Lutra lutra", "Vulpes vulpes", 
"Vulpes vulpes", "Vulpes vulpes", "Vulpes vulpes", "Lutra lutra", 
"Lutra lutra", "Lutra lutra", "Lutra lutra", "Lutra lutra", "Lutra lutra", 
"Lutra lutra", "Lutra lutra", "Lutra lutra", "Vulpes vulpes", 
"Vulpes vulpes", "Vulpes vulpes"), Detection = c(0, 0, 0, 0, 
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
), Elevation = c(207, 213, 213, 213, 213, 213, 213, 213, 189, 
189, 189, 189, 169, 169, 169, 169, 169, 169, 169, 169, 169, 169, 
169, 169, 169, 169, 169, 169, 169, 169, 169, 169, 169, 169, 186, 
186, 186, 186, 186, 186, 186, 186, 186, 222, 222, 222)), row.names = c(NA, 
-46L), class = "data.frame")

如果它是 Vulpes vulpes 的新数据框，我想要如下所示的内容:

Camera.Trap.Name Sampling.Event Photo.Date  Species_name Detection Elevation
CT-Tst-5-1        Olney 7       2020-05-02  Vulpes vulpes      1       169
CT-Tst-8-1        Olney 7       2020-04-28   Lutra lutra       0       186
CT-Tst-8-1        Olney 7       2020-04-29   Lutra lutra       0       186

我试图创建独特物种名称的列表，并创建一个遍历数据框的循环，如果名称匹配，则将检测值更改为 1，最后为该物种创建一个新的更新数据框。这些都非常不成功，因此将不胜感激所有帮助。 谢谢

Answer 1

您描述的方法是正确的。但是，在修改Detection 值之前需要先复制数据，这样就不会更改原始数据及其后续副本。

s = unique(df$Species_name)   # list of unique species names

m = list()   # empty list (to fill with copies of the data)

for (i in s) {
  temp = df  # make a copy of the data frame

   # change Detection to 1 where species name match
  temp$Detection[temp$Species_name==i] = 1 

  m[[i]] = temp # place the new data in the array
}

(temp变量只是为了让代码更易读，可以直接复制到m[[i]])

现在您将 m 作为包含 2 个数据帧的列表:

> m[["Vulpes vulpes"]]
....
12       CT-Tst-3-1        Olney 3 2019-11-16 Vulpes vulpes         1       189
13       CT-Tst-5-1        Olney 5 2020-03-24 Vulpes vulpes         1       169
14       CT-Tst-5-1        Olney 5 2020-03-25   Lutra lutra         0       169
15       CT-Tst-5-1        Olney 5 2020-03-26 Vulpes vulpes         1       169

和

> m[['Lutra lutra']]
....
12       CT-Tst-3-1        Olney 3 2019-11-16 Vulpes vulpes         0       189
13       CT-Tst-5-1        Olney 5 2020-03-24 Vulpes vulpes         0       169
14       CT-Tst-5-1        Olney 5 2020-03-25   Lutra lutra         1       169
15       CT-Tst-5-1        Olney 5 2020-03-26 Vulpes vulpes         0       169