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法律研究如何從 R 資料框列中提取不以特定字元開頭和結尾的值？
有時我們只想根據列的初始值和結束值提取資料列的值，該列包含字串，或者有時包含字串的列的值以一些額外的字元記錄，我們想提取這些值。為此，我們可以使用帶單個方括號的 grepl 的否定。
示例
考慮以下資料框 -
> x2<-c("Alabama", "Alaska", "American Samoa", "Arizona", "Arkansas", "California",
"Colorado", "Connecticut", "Delaware", "District of Columbia", "Florida", "Georgia",
"Guam", "Hawaii", "Idaho", "Illinois", "Indiana", "Iowa", "Kansas", "Kentucky",
"Louisiana", "Maine", "Maryland", "Massachusetts", "Michigan", "Minnesota", "Minor
Outlying Islands", "Mississippi", "Missouri", "Montana", "Nebraska", "Nevada", "New
Hampshire", "New Jersey", "New Mexico", "New York", "North Carolina", "North
Dakota", "Northern Mariana Islands", "Ohio", "Oklahoma", "Oregon", "Pennsylvania",
"Puerto Rico", "Rhode Island", "South Carolina", "South Dakota", "Tennessee", "Texas",
"U.S. Virgin Islands", "Utah", "Vermont", "Virginia", "Washington", "West Virginia",
"Wisconsin", "Wyoming")> df2<-data.frame(x2) > head(df2,20)
輸出
x2 1 Alabama 2 Alaska 3 American Samoa 4 Arizona 5 Arkansas 6 California 7 Colorado 8 Connecticut 9 Delaware 10 District of Columbia 11 Florida 12 Georgia 13 Guam 14 Hawaii 15 Idaho 16 Illinois 17 Indiana 18 Iowa 19 Kansas 20 Kentucky
查詢既不以 A 開頭也不以 a 結尾的州 -
> df2[!grepl("^A|a$",df2$x2),]輸出
[1] Colorado Connecticut Delaware [4] Guam Hawaii Idaho [7] Illinois Kansas Kentucky [10] Maine Maryland Massachusetts [13] Michigan Minor Outlying Islands Mississippi [16] Missouri New Hampshire New Jersey [19] New Mexico New York Northern Mariana Islands [22] Ohio Oregon Puerto Rico [25] Rhode Island Tennessee Texas [28] U.S. Virgin Islands Utah Vermont [31] Washington Wisconsin Wyoming 57 Levels: Alabama Alaska American Samoa Arizona Arkansas ... Wyoming
讓我們看看另一個例子 -
> x1<-
c("Indiaaa","Chinaaa","Russiaa","Canadaaa","Indonesiaaa","Croatiaaa","Mauritaniaaa","
Albaniaaa","Angolaaa","Armeniaaa","Malaysiaaa","Maltaaa","Boliviaaa","Burmaaa","Pa
nama","Romaniaa","Saudi-Arabia","Serbiaaa","Syriaaa","Tongaaa","Koreaaa","Libya")> y1<-sample(1:10,22,replace=TRUE) > df1<-data.frame(x1,y1) > df1
輸出
x1 y1 1 Indiaaa 6 2 Chinaaa 1 3 Russiaa 9 4 Canadaaa 7 5 Indonesiaaa 7 6 Croatiaaa 3 7 Mauritaniaaa 6 8 Albaniaaa 2 9 Angolaaa 10 10 Armeniaaa 10 11 Malaysiaaa 7 12 Maltaaa 3 13 Boliviaaa 2 14 Burmaaa 10 15 Panama 1 16 Romaniaa 10 17 Saudi-Arabia 10 18 Serbiaaa 8 19 Syriaaa 10 20 Tongaaa 5 21 Koreaaa 7 22 Libya 8
> df1[!grepl("^A|aa$",df1$x1),]輸出
x1 y1 15 Panama 1 17 Saudi-Arabia 10 22 Libya 8
> df1[!grepl("^S|aa$",df1$x1),]輸出
x1 y1 15 Panama 1 22 Libya 8
> df1[!grepl("^B|aa$",df1$x1),]輸出
x1 y1 15 Panama 1 17 Saudi-Arabia 10 22 Libya 8
> df1[!grepl("^P|aa$",df1$x1),]輸出
x1 y1 17 Saudi-Arabia 10 22 Libya 8
> df1[!grepl("^L|aa$",df1$x1),]輸出
x1 y1 15 Panama 1 17 Saudi-Arabia 10
更新於： 2020-09-07
75 次瀏覽
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