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1、4DataframesLearninghowtohandleyourdata,howtoenterthemintothecomputer,andhowtoreadthemintoRareamongthemostimportanttopicsyouwillneedtomaster.Rhandlesdatainobjectsknownasdataframes.Adataframeisanobjectwithrowsandcolumns(abitlikeamatrix).Therowscontaindifferento
2、bservationsfromyourstudy,ormeasurementsfromyourexperiment(thesearesometimescalledcases).Thecolumnscontainthevaluesofdifferentvariables(theseareoftencalledfields).Thevaluesinthebodyofamatrixcanonlybenumbers,butthevaluesinthebodyofadataframecanbenumbers,buttheyc
3、ouldalsobetext(e.g.thenamesoffactorlevelsforcategoricalvariables,likemaleorfemaleinavariablecalledgender),theycouldbecalendardates(e.g.23/5/04),ortheycouldbelogicalvariables(TRUEorFALSE).Hereisaspreadsheetintheformofadataframewithsevenvariables,theleftmostofw
4、hichcomprisestherownames,andothervariablesarenumeric(Area,Slope,SoilpHandWormDensity),categorical(FieldNameandVegetation)orlogical(Dampiseithertrue=Torfalse=F).FieldNameAreaSlopeVegetationSoilpHDampWormDensityNash’sField3.611Grassland4.1F4SilwoodBottom5.12Ara
5、ble5.2F7NurseryField2.83Grassland4.3F2RushMeadow2.45Meadow4.9T5Gunness’Thicket3.80Scrub4.2F6OakMead3.12Grassland3.9F2ChurchField3.53Grassland4.2F3Ashurst2.10Arable4.8F4TheOrchard1.90Orchard5.7F9RookerySlope1.54Grassland5T7GardenWood2.910Scrub5.2F8NorthGravel3
6、.31Grassland4.1F1SouthGravel3.72Grassland4F2ObservatoryRidge1.86Grassland3.8F0PondField4.10Meadow5T6WaterMeadow3.90Meadow4.9T8Cheapside2.28Scrub4.7T4(Continued)TheRBook,SecondEdition.MichaelJ.Crawley.©2013JohnWiley&Sons,Ltd.Published2013byJohnWiley&Sons,Ltd.1
7、60THERBOOK(Continued)FieldNameAreaSlopeVegetationSoilpHDampWormDensityPoundHill4.42Arable4.5F5GravelPit2.91Grassland3.5F1FarmWood0.810Scrub5.1T3Perhapsthemostimportantthingaboutanalysingyourowndataproperlyisgettingyourdataframeabsolutelyright.Theexpectationis
8、thatyouwillhaveusedaspreadsheetsuchasExceltoenterandeditthedata,andthatyouwillhaveusedplotstocheckforerrors.Thethingthattakessomepracticeislearningexactlyhowtoputyournumbersintothespreads
