working with your data

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1、CHAPTER3WorkingwithYourData3.1CreatingandRedefiningVariables783.2UsingSASFunctions803.3SelectedSASCharacterFunctions823.4SelectedSASNumericFunctions843.5UsingIF-THENStatements863.6GroupingObservationswithIF-THEN/ELSEStatements883.7SubsettingYourData903.8WorkingwithSASDates923.9SelectedDateIn

2、formats,Functions,andFormats943.10UsingtheRETAINandSumStatements963.11SimplifyingProgramswithArrays983.12UsingShortcutsforListsofVariableNames10078TheLittleSASBook3.1CreatingandRedefiningVariablesIfsomeoneweretocompilealistofthemostpopularthingstodowithSASsoftware,creatingandredefiningvariab

3、leswouldsurelybenearthetop.Fortunately,SASisflexibleandusesacommonsenseapproachtothesetasks.Youcreateandredefinevariableswithassignmentstatementsusingthisbasicform:variable=expression;Ontheleftsideoftheequalsignisavariablename,eitherneworold.Ontherightsideoftheequalsignmayappearaconstant,ano

4、thervariable,oramathematicalexpression.Hereareexamplesofthesebasictypesofassignmentstatements:TypeofexpressionAssignmentstatementnumericconstantQwerty=10;characterconstantQwerty='ten';avariableQwerty=OldVar;additionQwerty=OldVar+10;subtractionQwerty=OldVar-10;multiplicationQwerty=OldVar*10;d

5、ivisionQwerty=OldVar/10;exponentiationQwerty=OldVar**10;WhetherthevariableQwertyisnumericorcharacterdependsontheexpressionthatdefinesit.Whentheexpressionisnumeric,Qwertywillbenumeric;whenitischaracter,Qwertywillbecharacter.Whendecidinghowtointerpretyourexpression,SASfollowsthestandardmathema

6、ticalrulesofprecedence:SASperformsexponentiationfirst,thenmultiplicationanddivision,followedbyadditionandsubtraction.Youcanuseparenthesestooverridethatorder.HerearetwosimilarSASstatementsshowingthatacoupleofparenthesescanmakeabigdifference:AssignmentstatementResultx=10*4+3**2;x=49x=10*(4+3**

7、2);x=130WhileSAScanreadexpressionswithorwithoutparentheses,peopleoftencan’t.Ifyouuseparentheses,yourprogramswillbealoteasiertoread.ExampleThefollowingrawdataarefromasurveyofhomegardeners.Gardenerswereaskedtoestimatethenumberofpoundstheyharvestedfor