MATLAB Data Import and Export - Agricultural & Applied Economics

282 Pages·2011·1.11 MB·English

MATLAB®
Data Import and Export
R2011b
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MATLAB®DataImportandExport
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Revision History
September2009 Onlineonly NewforMATLAB7.9(Release2009b)
March2010 Onlineonly RevisedforMATLAB7.10(Release2010a)
September2010 Onlineonly RevisedforMATLAB7.11(Release2010b)
April2011 Onlineonly RevisedforMATLAB7.12(Release2011a)
September2011 Onlineonly RevisedforMATLAB7.13(Release2011b)
Contents
Supported File Formats
1
SupportedFileFormats ............................ 1-2
Importing Data
2
RecommendedMethodsforImportingData .......... 2-2
ToolsthatImportMultipleFileFormats ............... 2-2
ImportingSpecificFileFormats ...................... 2-3
ImportingDatainOtherFormats .................... 2-4
FindingFiles ..................................... 2-4
ProcessingaSequenceofFiles ....................... 2-5
TipsforUsingtheImportWizard .................... 2-5
ImportingMAT-Files ............................... 2-11
ViewtheContentsofaMAT-File ..................... 2-11
WaystoLoadDatafromaMAT-File .................. 2-12
LoadPartofaVariablefromaMAT-File .............. 2-13
Troubleshooting: LoadingVariableswithinaFunction ... 2-16
ImportingTextDataFiles .......................... 2-18
WaystoImportTextFiles .......................... 2-18
ImportNumericDatafromaTextFile ................ 2-20
ImportNumericDataandHeaderTextfromaTextFile .. 2-21
ImportMixedTextandNumericDatafromaTextFile ... 2-25
ImportLargeTextFiles ............................ 2-26
ImportDatafromaNonrectangularTextFile .......... 2-27
ImportTextDataFileswithLow-LevelI/O ............ 2-29
ImportingXMLDocuments ......................... 2-37
WhatIsanXMLDocumentObjectModel(DOM)? ....... 2-37
Example—FindingTextinanXMLFile .............. 2-38
iii
ImportingSpreadsheets ............................ 2-41
WaystoImportSpreadsheets ........................ 2-41
SelectSpreadsheetDataInteractively ................. 2-42
ImportaWorksheetorRangewithxlsread ............. 2-44
ImportAllWorksheetsinaFilewithimportdata ........ 2-46
SystemRequirementsforImportingSpreadsheets ...... 2-47
WhentoConvertDatesfromExcelFiles ............... 2-48
ImportingScientificDataFiles ..................... 2-50
ImportingCommonDataFileFormat(CDF)Files ....... 2-50
Importing Network Common Data Form (NetCDF)
Files .......................................... 2-57
Importing Flexible Image Transport System (FITS)
Files .......................................... 2-64
ImportingHierarchicalDataFormat(HDF5)Files ...... 2-66
ImportingHierarchicalDataFormat(HDF4)Files ...... 2-73
ImportingImages .................................. 2-104
GettingInformationaboutImageFiles ................ 2-104
ReadingImageDataandMetadatafromTIFFFiles ..... 2-105
ImportingAudioandVideo ......................... 2-108
GettingInformationaboutAudioorVideoFiles ......... 2-108
ReadingAudioFiles ............................... 2-109
RecordingandPlayingAudio ........................ 2-109
ReadingVideoFiles ............................... 2-112
ImportingBinaryDatawithLow-LevelI/O ........... 2-117
Low-LevelFunctionsforImportingData .............. 2-117
ReadingBinaryDatainaFile ....................... 2-118
ReadingPortionsofaFile ........................... 2-120
ReadingFilesCreatedonOtherSystems .............. 2-123
OpeningFileswithDifferentCharacterEncodings ...... 2-124
Exporting Data
3
ExportingtoMAT-Files ............................ 3-2
WaystoSaveWorkspaceVariables ................... 3-2
iv Contents
SavePartofaVariableinaMAT-File ................. 3-3
SaveStructureFieldsasSeparateVariables ........... 3-5
MAT-FileVersions ................................ 3-6
ExportingtoTextDataFiles ........................ 3-8
WritingtoDelimitedDataFiles ...................... 3-8
WritingtoaDiaryFile ............................. 3-11
WritingtoTextDataFileswithLow-LevelI/O .......... 3-12
ExportingtoXMLDocuments ....................... 3-20
CreatinganXMLFile .............................. 3-20
UpdatinganExistingXMLFile ...................... 3-22
ExportingtoExcelSpreadsheets .................... 3-24
WritingtoaSpreadsheetFile ....................... 3-24
AddingaNewWorksheet ........................... 3-24
FileFormatsthatxlswriteSupports .................. 3-25
ConvertingDates ................................. 3-25
FormattingCellsinExcelFiles ...................... 3-26
ExportingtoScientificDataFiles ................... 3-28
ExportingtoCommonDataFileFormat(CDF)Files ..... 3-28
Exporting to Network Common Data Form (NetCDF)
Files .......................................... 3-30
ExportingtoHierarchicalDataFormat(HDF5)Files .... 3-39
ExportingtoHierarchicalDataFormat(HDF4)Files .... 3-49
ExportingtoImages ............................... 3-60
ExportingImageDataandMetadatatoTIFFFiles ...... 3-60
ExportingtoAudioandVideo ...................... 3-76
ExportingtoAudioFiles ............................ 3-76
ExportingVideotoAVIFiles ........................ 3-76
ExportingBinaryDatawithLow-LevelI/O ........... 3-78
Low-LevelFunctionsforExportingData .............. 3-78
WritingBinaryDatatoaFile ....................... 3-79
OverwritingorAppendingtoanExistingFile .......... 3-79
CreatingaFileforUseonaDifferentSystem .......... 3-81
OpeningFileswithDifferentCharacterEncodings ...... 3-82
WritingandReadingComplexNumbers ............... 3-83
v
CreatingTemporaryFiles .......................... 3-86
Memory-Mapping Data Files
4
OverviewofMemory-Mapping ...................... 4-2
WhatIsMemory-Mapping? ......................... 4-2
BenefitsofMemory-Mapping ........................ 4-2
WhentoUseMemory-Mapping ...................... 4-4
MaximumSizeofaMemoryMap ..................... 4-5
ByteOrdering .................................... 4-6
ThememmapfileClass ............................. 4-7
SettingProperties ................................. 4-7
ViewingProperties ................................ 4-8
ConstructingamemmapfileObject .................. 4-10
HowtoRunExamplesinThisSection ................. 4-10
ConstructingtheObjectwithDefaultPropertyValues ... 4-11
ChangingPropertyValues .......................... 4-11
SelectingtheFiletoMap ........................... 4-13
SettingtheStartoftheMappedRegion ............... 4-14
IdentifyingtheContentsoftheMappedRegion ......... 4-14
MappingoftheExampleFile ........................ 4-19
RepeatingaFormatScheme ......................... 4-21
SettingtheTypeofAccess .......................... 4-22
ReadingaMappedFile ............................. 4-24
Introduction ...................................... 4-24
ImprovingPerformance ............................ 4-24
Example1—ReadingaSingleDataType ............. 4-25
Example2—FormattingFileDataasaMatrix ......... 4-26
Example3—ReadingMultipleDataTypes ............ 4-27
Example4—ModifyingMapParameters .............. 4-28
WritingtoaMappedFile ........................... 4-30
Example—WritingtoaMappedFile ................. 4-30
DimensionsoftheDataField ........................ 4-31
WritingMatricestoaMappedFile ................... 4-33
vi Contents
SelectingAppropriateDataTypes .................... 4-35
WorkingwithCopiesoftheMappedData .............. 4-36
DeletingaMemoryMap ............................ 4-38
TheEffectofSharedDataCopiesOnPerformance ...... 4-38
Memory-MappingDemo ............................ 4-39
Introduction ...................................... 4-39
ThesendFunction ................................. 4-39
TheanswerFunction .............................. 4-41
RunningtheDemo ................................ 4-42
Internet File Access
5
DownloadingWebContentandFiles ................ 5-2
Example—UsingtheurlreadFunction ............... 5-2
Example—UsingtheurlwriteFunction ............... 5-3
CreatingandDecompressingZipArchives ........... 5-4
Example—UsingthezipFunction ................... 5-4
SendingEmail ..................................... 5-5
Example—UsingthesendmailFunction .............. 5-6
PerformingFTPFileOperations .................... 5-8
Example—RetrievingaFilefromanFTPServer ....... 5-8
Index
vii
viii Contents
1
Supported File Formats
1
Supported File Formats
Supported File Formats
The following table shows the file formats that you can import and export
from the MATLAB® application. The Import Wizard and the importdata
function support all listed formats, except:
• Motion JPEG 2000.
(cid:129) Platform-specific video.
(cid:129) netCDF.
(cid:129) H5.
(cid:129) TheImportWizardsupportsHDFfiles,butimportdatadoesnot.
Import Export
File Content Extension Description Function Function
MATLAB MAT Saved MATLAB load save
formatted data workspace
Text any White-space delimited load save-ascii
numbers
Delimited numbers dlmread dlmwrite
Delimited numbers, or textscan
a mix of strings and
numbers
Spreadsheet XLS Microsoft® Excel® xlsread xlswrite
worksheet
XLSX Formats supported on
XLSB Windows® systems with
XLSM Excel®2007orlater
ODS OpenDocument™ xlsread none
Spreadsheet, supported
on Windows systems
with Excel 2010 orlater
(OpenDocument is a
trademark of OASIS™,
1-2