readtable
基于文件创建表
语法
说明
T = readtable(filename,Name=Value)TextType 名称-值参量指定将文本数据作为字符向量或字符串数组导入。
T = readtable(filename,opts,Name=Value)readtable 对文本文件仅支持 ReadVariableNames、ReadRowNames、DateLocale 和 Encoding 名称-值参量，对电子表格文件仅支持 ReadVariableNames、ReadRowNames、Sheet 和 UseExcel 名称-值参量。
示例
将文本文件的内容导入表中。生成的表为文件中的每一列包含一个变量，并使用文件第一行中的条目作为变量名。
T = readtable("myCsvTable.dat")T=5×6 table
LastName Gender Age Height Weight Smoker
____________ ______ ___ ______ ______ ______
{'Smith' } {'M'} 38 71 176 1
{'Johnson' } {'M'} 43 69 163 0
{'Williams'} {'F'} 38 64 131 0
{'Jones' } {'F'} 40 67 133 0
{'Brown' } {'F'} 49 64 119 0
从包含数据间隙的文本文件创建表。默认情况下，readtable 会用适当的缺失值来填充间隙。
T = readtable("headersAndMissing.txt")T=5×6 table
LastName Gender Age Height Weight Smoker
___________ __________ ___ ______ ______ ______
{'Wu' } {'M' } 38 71 176 1
{'Johnson'} {'M' } 43 69 163 0
{'Sanchez'} {'F' } 38 64 131 0
{'Brown' } {'F' } NaN 67 133 0
{'Picard' } {0×0 char} NaN 64 119 0
要忽略有数据间隙的行，请指定 MissingRule 名称-值参量。
T = readtable("headersAndMissing.txt",MissingRule="omitrow")
T=3×6 table
LastName Gender Age Height Weight Smoker
___________ ______ ___ ______ ______ ______
{'Wu' } {'M'} 38 71 176 1
{'Johnson'} {'M'} 43 69 163 0
{'Sanchez'} {'F'} 38 64 131 0
使用导入选项对象配置 readtable 解释文件的方式。例如，使用导入选项对象仅读取文本文件的一部分内容。
首先，使用 detectImportOptions 创建一个导入选项对象来检测文本文件的各个方面，包括变量名称和类型、分隔符以及空白字符。在本例中，detectImportOptions 会创建一个 DelimitedTextImportOptions 对象。
opts = detectImportOptions("airlinesmall.csv")opts =
DelimitedTextImportOptions with properties:
Format Properties:
Delimiter: {','}
Whitespace: '\b\t '
LineEnding: {'\n' '\r' '\r\n'}
CommentStyle: {}
ConsecutiveDelimitersRule: 'split'
LeadingDelimitersRule: 'keep'
TrailingDelimitersRule: 'ignore'
EmptyLineRule: 'skip'
Encoding: 'ISO-8859-1'
Replacement Properties:
MissingRule: 'fill'
ImportErrorRule: 'fill'
ExtraColumnsRule: 'addvars'
Variable Import Properties: Set types by name using setvartype
VariableNames: {'Year', 'Month', 'DayofMonth' ... and 26 more}
VariableTypes: {'double', 'double', 'double' ... and 26 more}
SelectedVariableNames: {'Year', 'Month', 'DayofMonth' ... and 26 more}
VariableOptions: Show all 29 VariableOptions
Access VariableOptions sub-properties using setvaropts/getvaropts
VariableNamingRule: 'modify'
Location Properties:
DataLines: [2 Inf]
VariableNamesLine: 1
RowNamesColumn: 0
VariableUnitsLine: 0
VariableDescriptionsLine: 0
To display a preview of the table, use preview
通过修改导入选项对象来指定要导入的变量子集。然后，使用 readtable 和导入选项对象导入数据子集。
opts.SelectedVariableNames = ["TaxiIn","TaxiOut"]; T = readtable("airlinesmall.csv",opts);
基于包含第一行的变量名称和第一列的行名称的电子表格创建表。显示表的前五行和前四个变量。
T = readtable("patients.xls",ReadRowNames=true);
T(1:5,1:4)ans=5×4 table
Gender Age Location Height
__________ ___ _____________________________ ______
Smith {'Male' } 38 {'County General Hospital' } 71
Johnson {'Male' } 43 {'VA Hospital' } 69
Williams {'Female'} 38 {'St. Mary's Medical Center'} 64
Jones {'Female'} 40 {'VA Hospital' } 67
Brown {'Female'} 49 {'County General Hospital' } 64
使用电子表格的指定区域中的数据创建表。使用 C2 和 E6 两个对角之间的 5×3 矩形区域内的数据。不要将该区域的第一行用作变量名称。结果表改用默认变量名称。
T = readtable("patients.xls",Range="C2:E6",ReadVariableNames=false)
T=5×3 table
38 'County General Hospital' 71
43 'VA Hospital' 69
38 'St. Mary's Medical Center' 64
40 'VA Hospital' 67
49 'County General Hospital' 64
使用导入选项对象配置 readtable 解释文件的方式。例如，使用导入选项对象仅从电子表格文件中读取指定的变量。
首先，通过使用 detectImportOptions 检测电子表格文件的各个方面（包括变量名称和类型），从文件创建一个导入选项对象。在本例中，detectImportOptions 会创建一个 SpreadsheetImportOptions 对象。
opts = detectImportOptions("patients.xls")opts =
SpreadsheetImportOptions with properties:
Sheet Properties:
Sheet: ''
Replacement Properties:
MissingRule: 'fill'
ImportErrorRule: 'fill'
MergedCellColumnRule: 'placeleft'
MergedCellRowRule: 'placetop'
Variable Import Properties: Set types by name using setvartype
VariableNames: {'LastName', 'Gender', 'Age' ... and 7 more}
VariableTypes: {'char', 'char', 'double' ... and 7 more}
SelectedVariableNames: {'LastName', 'Gender', 'Age' ... and 7 more}
VariableOptions: Show all 10 VariableOptions
Access VariableOptions sub-properties using setvaropts/getvaropts
VariableNamingRule: 'modify'
Range Properties:
DataRange: 'A2' (Start Cell)
VariableNamesRange: 'A1'
RowNamesRange: ''
VariableUnitsRange: ''
VariableDescriptionsRange: ''
To display a preview of the table, use preview
通过修改导入选项对象来指定要导入的变量。然后，使用 readtable 和导入选项对象导入指定的变量。显示表的前 5 行。
opts.SelectedVariableNames = ["Systolic","Diastolic"]; T = readtable("patients.xls",opts); T(1:5,:)
ans=5×2 table
Systolic Diastolic
________ _________
124 93
109 77
125 83
117 75
122 80
将 JSON 文件的内容导入表中。
students.json 文件有三个同级节点，每个节点都包含相同的子节点和属性。
type students.json[
{
"ID": "S11305",
"Name": {
"FirstName": "Priya",
"LastName": "Thompson"
},
"Age": 18.0,
"Year": "Freshman",
"Address": {
"Street": "591 Spring Lane",
"City": "Natick",
"State": "MA"
},
"Major": "Computer Science",
"Minor": "English Literature"
},
{
"ID": "S23451",
"Name": {
"FirstName": "Conor",
"LastName": "Cole"
},
"Age": 18.0,
"Year": "Freshman",
"Address": {
"Street": "4641 Pearl Street",
"City": "San Francisco",
"State": "CA"
},
"Major": "Microbiology",
"Minor": "Public Health"
},
{
"ID": "S119323",
"Name": {
"FirstName": "Morgan",
"LastName": "Yang"
},
"Age": 21.0,
"Year": "Senior",
"Address": {
"Street": "30 Highland Road",
"City": "Detroit",
"State": "MI"
},
"Major": "Political Science"
}
]
首先，使用 detectImportOptions 创建一个 JSONImportOptions 对象，以检测 JSON 文件的各个方面。通过将 VariableSelectors 名称-值参量指定为 Street 对象键的 JSON 指针，仅将街道名称读取到表中。
opts = detectImportOptions("students.json",VariableSelectors="/Address/Street");
然后，使用 readtable 和导入选项对象导入指定的变量。
T = readtable("students.json",opts)T=3×1 table
Street
___________________
"591 Spring Lane"
"4641 Pearl Street"
"30 Highland Road"
将 XML 文件的内容导入表中。
students.xml 文件有三个名为 Student 的同级节点，每个节点都包含相同的子节点和属性。
type students.xml<?xml version="1.0" encoding="utf-8"?>
<Students>
<Student ID="S11305">
<Name FirstName="Priya" LastName="Thompson" />
<Age>18</Age>
<Year>Freshman</Year>
<Address>
<Street xmlns="https://www.mathworks.com">591 Spring Lane</Street>
<City>Natick</City>
<State>MA</State>
</Address>
<Major>Computer Science</Major>
<Minor>English Literature</Minor>
</Student>
<Student ID="S23451">
<Name FirstName="Conor" LastName="Cole" />
<Age>18</Age>
<Year>Freshman</Year>
<Address>
<Street xmlns="https://www.mathworks.com">4641 Pearl Street</Street>
<City>San Francisco</City>
<State>CA</State>
</Address>
<Major>Microbiology</Major>
<Minor>Public Health</Minor>
</Student>
<Student ID="S119323">
<Name FirstName="Morgan" LastName="Yang" />
<Age>21</Age>
<Year>Senior</Year>
<Address>
<Street xmlns="https://www.mathworks.com">30 Highland Road</Street>
<City>Detriot</City>
<State>MI</State>
</Address>
<Major>Political Science</Major>
</Student>
</Students>
首先，使用 detectImportOptions 创建一个 XMLImportOptions 对象来检测 XML 文件的各个方面。通过将 VariableSelectors 名称-值参量指定为 Street 元素节点的 XPath 表达式，仅将街道名称读入表中。通过设置 RegisteredNamespaces 名称-值参量，将自定义命名空间前缀注册到现有命名空间 URL。
opts = detectImportOptions("students.xml",RegisteredNamespaces=["myPrefix","https://www.mathworks.com"], ... VariableSelectors="//myPrefix:Street");
然后，使用 readtable 和导入选项对象导入指定的变量。
T = readtable("students.xml",opts)T=3×1 table
Street
___________________
"591 Spring Lane"
"4641 Pearl Street"
"30 Highland Road"
将 Microsoft Word 文档中的表导入 MATLAB 中的表。在本例中，文档包含两个表，第二个表包含合并的单元格。通过设置 TableIndex 名称-值参量读取第二个表。通过设置 MergedCellColumnRule 名称-值参量，跳过包含合并列的单元格的行。
filename = "MaintenanceReport.docx"; T = readtable(filename,TableIndex=2,MergedCellColumnRule="omitrow")
T=3×5 table
Description Category Urgency Resolution Cost
_____________________________________________________________________ ____________________ ________ __________________ ________
"Items are occasionally getting stuck in the scanner spools." "Mechanical Failure" "Medium" "Readjust Machine" "$45"
"Loud rattling and banging sounds are coming from assembler pistons." "Mechanical Failure" "Medium" "Readjust Machine" "$35"
"There are cuts to the power when starting the plant." "Electronic Failure" "High" "Full Replacement" "$16200"
您也可以使用 TableSelector 名称-值参量选择具有 XPath 选择器的表。要选择 Microsoft Word 文档中包含文本“Descriptio”的表，请使用 XPath 选择器 "//w:tbl[contains(.,'Description')]"。
T = readtable(filename, ... TableSelector="//w:tbl[contains(.,'Description')]", ... MergedCellColumnRule="omitrow")
T=3×5 table
Description Category Urgency Resolution Cost
_____________________________________________________________________ ____________________ ________ __________________ ________
"Items are occasionally getting stuck in the scanner spools." "Mechanical Failure" "Medium" "Readjust Machine" "$45"
"Loud rattling and banging sounds are coming from assembler pistons." "Mechanical Failure" "Medium" "Readjust Machine" "$35"
"There are cuts to the power when starting the plant." "Electronic Failure" "High" "Full Replacement" "$16200"
使用 XPath 选择器 "//TABLE[contains(.,'readtable')]" 从 URL https://www.mathworks.com/help/matlab/text-files.html 中导入第一个包含文本 "readtable" 的表。该表没有标题行，因此将 ReadVariableNames 名称-值参量设置为 false。
url = "https://www.mathworks.com/help/matlab/text-files.html"; T = readtable(url,TableSelector="//TABLE[contains(.,'readtable')]", ... ReadVariableNames=false)
T=4×2 table
"readtable" "Create table from file"
"writetable" "Write table to file"
"readtimetable" "Create timetable from file"
"writetimetable" "Write timetable to file"
