readtable
基于文件创建表
语法
说明
T = readtable(filename,Name=Value)ReadVariableNames 名称-值参量，可以将文件的第一行作为变量名称或数据读取。
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
Var1 Var2 Var3
____ _____________________________ ____
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 XML 文件的内容导入表中。
students.xml 文件有七个名为 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>
<Student ID="S201351">
<Name FirstName="Salim" LastName="Copeland" />
<Age>19</Age>
<Year>Sophomore</Year>
<Address>
<Street xmlns="https://www.mathworks.com">3388 Moore Avenue</Street>
<City>Fort Worth</City>
<State>TX</State>
</Address>
<Major>Business</Major>
<Minor>Japanese Language</Minor>
</Student>
<Student ID="S201351">
<Name FirstName="Salim" LastName="Copeland" />
<Age>20</Age>
<Year>Sophomore</Year>
<Address>
<Street xmlns="https://www.mathworks.com">3388 Moore Avenue</Street>
<City>Fort Worth</City>
<State>TX</State>
</Address>
<Major>Business</Major>
<Minor>Japanese Language</Minor>
</Student>
<Student ID="54600">
<Name FirstName="Dania" LastName="Burt" />
<Age>22</Age>
<Year>Senior</Year>
<Address>
<Street xmlns="https://www.mathworks.com">22 Angie Drive</Street>
<City>Los Angeles</City>
<State>CA</State>
</Address>
<Major>Mechanical Engineering</Major>
<Minor>Architecture</Minor>
</Student>
<Student ID="453197">
<Name FirstName="Rikki" LastName="Gunn" />
<Age>21</Age>
<Year>Junior</Year>
<Address>
<Street xmlns="https://www.mathworks.com">65 Decatur Lane</Street>
<City>Trenton</City>
<State>ME</State>
</Address>
<Major>Economics</Major>
<Minor>Art History</Minor>
</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=7×1 table
Street
___________________
"591 Spring Lane"
"4641 Pearl Street"
"30 Highland Road"
"3388 Moore Avenue"
"3388 Moore Avenue"
"22 Angie Drive"
"65 Decatur Lane"
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
Var1 Var2
________________ ____________________________
"readtable" "Create table from file"
"writetable" "Write table to file"
"readtimetable" "Create timetable from file"
"writetimetable" "Write timetable to file"
