資料結構
網路
關係資料庫管理系統
作業系統
Java
MS Excel
iOS
HTML
CSS
Android
Python
C 程式設計
C++
C#
MongoDB
MySQL
Javascript
PHP
物理學
化學
生物學
數學
英語
經濟學
心理學
社會學
服裝設計
法律研究在 R 中提取字串向量元素，直到固定數量的字元。
為了在 R 中提取字串向量元素，直到固定數量的字元，我們可以使用基礎 R 的 substring 函式。
例如，如果我們有一個字串向量 X，其中包含 100 個字串值，並且我們想找到每個值的第一個五個字元，那麼我們可以使用如下命令：
substring(X,1,5)
示例 1
以下程式碼片段建立了一個示例資料框：
x1<-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")
x1建立了以下資料框
[1] "Alabama" "Alaska" [3] "American Samoa" "Arizona" [5] "Arkansas" "California" [7] "Colorado" "Connecticut" [9] "Delaware" "District of Columbia" [11] "Florida" "Georgia" [13] "Guam" "Hawaii" [15] "Idaho" "Illinois" [17] "Indiana" "Iowa" [19] "Kansas" "Kentucky" [21] "Louisiana" "Maine" [23] "Maryland" "Massachusetts" [25] "Michigan" "Minnesota" [27] "Minor Outlying Islands" "Mississippi" [29] "Missouri" "Montana" [31] "Nebraska" "Nevada" [33] "New Hampshire" "New Jersey" [35] "New Mexico" "New York" [37] "North Carolina" "North Dakota" [39] "Northern Mariana Islands" "Ohio" [41] "Oklahoma" "Oregon" [43] "Pennsylvania" "Puerto Rico" [45] "Rhode Island" "South Carolina" [47] "South Dakota" "Tennessee" [49] "Texas" "U.S. Virgin Islands" [51] "Utah" "Vermont" [53] "Virginia" "Washington" [55] "West Virginia" "Wisconsin" [57] "Wyoming"
為了找到上面建立的資料框中 x1 中每個值的第一個兩個字元，請將以下程式碼新增到上述程式碼片段中：
x1<-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")
substring(x1,1,2)輸出
如果您將以上所有給定的程式碼片段作為一個程式執行，它將生成以下輸出：
[1] "Al" "Al" "Am" "Ar" "Ar" "Ca" "Co" "Co" "De" "Di" "Fl" "Ge" "Gu" "Ha" "Id" [16] "Il" "In" "Io" "Ka" "Ke" "Lo" "Ma" "Ma" "Ma" "Mi" "Mi" "Mi" "Mi" "Mi" "Mo" [31] "Ne" "Ne" "Ne" "Ne" "Ne" "Ne" "No" "No" "No" "Oh" "Ok" "Or" "Pe" "Pu" "Rh" [46] "So" "So" "Te" "Te" "U." "Ut" "Ve" "Vi" "Wa" "We" "Wi" "Wy"
示例 2
以下程式碼片段建立了一個示例資料框：
x2<-c("Austria", "Belgium", "Bulgaria", "Croatia", "Cyprus", "Czechia",
"Denmark", "Estonia", "Finland", "France", "Germany", "Greece", "Hungary",
"Ireland", "Italy", "Latvia", "Lithuania", "Luxembourg", "Malta",
"Netherlands", "Poland", "Portugal", "Romania", "Slovakia", "Slovenia",
"Spain", "Sweden")
x2建立了以下資料框
[1] "Austria" "Belgium" "Bulgaria" "Croatia" "Cyprus" [6] "Czechia" "Denmark" "Estonia" "Finland" "France" [11] "Germany" "Greece" "Hungary" "Ireland" "Italy" [16] "Latvia" "Lithuania" "Luxembourg" "Malta" "Netherlands" [21] "Poland" "Portugal" "Romania" "Slovakia" "Slovenia" [26] "Spain" "Sweden"
為了找到上面建立的資料框中 x2 中每個值的第一個兩個字元，請將以下程式碼新增到上述程式碼片段中：
x2<-c("Austria", "Belgium", "Bulgaria", "Croatia", "Cyprus", "Czechia",
"Denmark", "Estonia", "Finland", "France", "Germany", "Greece", "Hungary",
"Ireland", "Italy", "Latvia", "Lithuania", "Luxembourg", "Malta",
"Netherlands", "Poland", "Portugal", "Romania", "Slovakia", "Slovenia",
"Spain", "Sweden")
substring(x2,1,2)輸出
如果您將以上所有給定的程式碼片段作為一個程式執行，它將生成以下輸出：
[1] "Au" "Be" "Bu" "Cr" "Cy" "Cz" "De" "Es" "Fi" "Fr" "Ge" "Gr" "Hu" "Ir" "It" [16] "La" "Li" "Lu" "Ma" "Ne" "Po" "Po" "Ro" "Sl" "Sl" "Sp" "Sw"
示例 3
以下程式碼片段建立了一個示例資料框：
x3<-c("Cuba", "Cyprus", "Czech Republic", "Djibouti", "Dominica", "Dominican
Republic", "East Timor", "Ecuador", "Egypt", "El Salvador", "Equatorial
Guinea", "Eritrea", "Estonia", "Ethiopia", "Fiji", "Finland", "France",
"Metropolitan", "French Guiana", "Gambia", "Georgia", "Germany", "Ghana",
"Greenland", "Grenada", "Guatemala", "Honduras", "Hong Kong", "Hungary",
"Iceland", "India", "Indonesia", "Iran", "Iraq", "Ireland", "Israel", "Italy",
"Jamaica", "Japan", "Jordan", "Kazakhstan", "Kenya", "Mozambique", "Namibia",
"Nepal", "Netherlands", "Nigeria", "Norway", "Oman", "Paraguay", "Peru",
"Philippines")
x3建立了以下資料框
[1] "Cuba" "Cyprus" "Czech Republic" [4] "Djibouti" "Dominica" "Dominican Republic" [7] "East Timor" "Ecuador" "Egypt" [10] "El Salvador" "Equatorial Guinea" "Eritrea" [13] "Estonia" "Ethiopia" "Fiji" [16] "Finland" "France" "Metropolitan" [19] "French Guiana" "Gambia" "Georgia" [22] "Germany" "Ghana" "Greenland" [25] "Grenada" "Guatemala" "Honduras" [28] "Hong Kong" "Hungary" "Iceland" [31] "India" "Indonesia" "Iran" [34] "Iraq" "Ireland" "Israel" [37] "Italy" "Jamaica" "Japan" [40] "Jordan" "Kazakhstan" "Kenya" [43] "Mozambique" "Namibia" "Nepal" [46] "Netherlands" "Nigeria" "Norway" [49] "Oman" "Paraguay" "Peru" [52] "Philippines"
為了找到上面建立的資料框中 x3 中每個值的第一個兩個字元，請將以下程式碼新增到上述程式碼片段中：
x3<-c("Cuba", "Cyprus", "Czech Republic", "Djibouti", "Dominica", "Dominican
Republic", "East Timor", "Ecuador", "Egypt", "El Salvador", "Equatorial
Guinea", "Eritrea", "Estonia", "Ethiopia", "Fiji", "Finland", "France",
"Metropolitan", "French Guiana", "Gambia", "Georgia", "Germany", "Ghana",
"Greenland", "Grenada", "Guatemala", "Honduras", "Hong Kong", "Hungary",
"Iceland", "India", "Indonesia", "Iran", "Iraq", "Ireland", "Israel", "Italy",
"Jamaica", "Japan", "Jordan", "Kazakhstan", "Kenya", "Mozambique", "Namibia",
"Nepal", "Netherlands", "Nigeria", "Norway", "Oman", "Paraguay", "Peru",
"Philippines")
substring(x3,1,2)輸出
如果您將以上所有給定的程式碼片段作為一個程式執行，它將生成以下輸出：
[1] "Cu" "Cy" "Cz" "Dj" "Do" "Do" "Ea" "Ec" "Eg" "El" "Eq" "Er" "Es" "Et" "Fi" [16] "Fi" "Fr" "Me" "Fr" "Ga" "Ge" "Ge" "Gh" "Gr" "Gr" "Gu" "Ho" "Ho" "Hu" "Ic" [31] "In" "In" "Ir" "Ir" "Ir" "Is" "It" "Ja" "Ja" "Jo" "Ka" "Ke" "Mo" "Na" "Ne" [46] "Ne" "Ni" "No" "Om" "Pa" "Pe" "Ph"
更新於: 2021年11月2日
473 次瀏覽
廣告