A Modern Approach to Regression with R-SASPrimerChapters1to8.pdf

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1、CharlesLindsey&ElizabethYoungAModernApproachtoRegressionwithRSASPrimerJune8,20091.Introduction1.1BuildingValidModelsSASworkswiththreetypesofcommands,orstepsastheSASliteraturecallsthem:data,proc,andoption.DatastepsreaddataintoSASandperformelementaryoperationsonth

2、edata.Procstepsperformmoresophisticatedoperationsonthedata,includingstatisticalanalysis.OptionstepssetattributesoftheSASsession,suchasthenumberofcolumnsusedforoutputandthedefaultcolorofpointsingraphics.Thedataandprocstepsaremadeupofcomponentstatements.Thesestate

3、mentsaresimilartotheonelinecommandsinStata.Wemayviewthedataandprocstepsasbatchesofstatements.TheSASliteraturereferstotheoptionsstepsasstatementsaswell,sincetheireffectsareatomicandstraightforward.IntheStataprimerwefocusedonexplainingindividualstatements.Duetothe

4、setupoftheSASlanguage,wewilldiscussourprogramsintermsofdataandprocstepsandoptionsstatements.Weshouldbeconsistentlythorough,butsomebrevitymayberequiredforreadability.Wenotethatourgraphicsareformulatedusingthe“charactercell”unit.ThisisthepixelsizethatSASprovidesfo

5、rdrawingasinglecharacter.ItisdependentonthepixelsizeoftheSASwindow.InrenderingthegraphicswegenerallyhaveSASmaximizedina1024x768screenresolutionenvironment.Ingeneral,thesizeofelementsofourgraphicswillvarydependingonwhetherthewindowismaximizedandwhattheoverallscre

6、enresolutionis.Sodependingonyourdesktopenvironment,yourgraphicsmayappeardifferent.Youcanexperimentwiththe“h=”optionspecificationintheaxisstatementsandothersizespecificationstomakethegraphicsvisuallyclearinyourenvironment.ThereareotherwaystoformulategraphicsinSAS

7、thanthe“charactercell”,butthe“charactercell”formulationisthedefault.Forsimplicitywewillstickwithitsuse.ItshouldalsobenotedthattheseprogramswerecreatedunderSASversion9.2.TheymayprovidedifferentresultsunderearlierorlaterversionsofSAS.1.2MotivatingExamplesWebeginwi

8、ththefootballexamplethatgivesusfigure1.1.Firstwereadinthedatawiththeprocstepimport.ThissavesthedataintheSASdatasetmyfootb.Thenamesofthedataareobtainedbythegetnamessta