Theyarestoredwithin ourdataframeinanobjectincalledtherownamesvector. Notethatthequotes aroundthemshowthattheyarestoredascharacters,notasnumbers. Sotheycannot beabbreviatedsimply Row namescanalsobecharactervaluesthatareeasiertoidentify,suchas "Ann","Bob","Carla". Thesearereferredtoas mydata[rows,columns].
Therearemanywaystoselectobservations rows fromadataframe. Forexample,togetsummarystatisticsonallrowsforall columns,usesummary mydata. Youcansubstituteanyoftheexamplesbelowtochoose asubsetofobservations. Thefactthatthecolumnpositionafter thecommaisblanktellsRtouseallthevariables. Toselectmorethanonevariableusingindexes,youmustcombinethemintoanumeric vectorusingthecombineorcfunction.
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Somydata[ c 5,6,7,8 , ]selects rows5through8,whichhappentobethemales. Thecolonoperator":"cangeneratea numericvectordirectly,somydata[, ]selectsthesameobservations. The colonoperatorcanabbreviatethisaswell,butit'stricky. Youuse itintheform,mydata[I ,]showingRthatyouwanttheminussigntoapplytothe justthesetofnumbers1,2,3,4. Youcanselectobservationsbynameinquotes,asinmydata[ "1", ]or mydata["Ann", ] ifyoucreatedsuchrownames,moreonthatlater. Ifyouhave morethanonename,youmustcombinethemintoasinglecharactervectorusingthe combineorcfunction.
Forexample, mydata[ c "1","2","3","4" , ]or mydata[ c "Ann","Carla","Bob","Sue" , ] Notethatevenifyournamesappeartobenumbers,theyarestillstoredcharacters. So youcannotabbreviatethemusingtheform However,youcouldgeneratethem usingthecolonoperatorandforcethemtobecomecharacterusingthe as. R Program to Select Observations. So this excludes the females in rows 1 through 4. The isolate function is used to apply the minus to 1,2,3,4 and prevent -1,0,1,2,3,4.
Otherwise how would you store the 5,6,7,8 values in a data frame that has 8 rows? Note that even though happyGuys is a variable name, it is not used in quotes. A logical comparison creates a logical vector that has a length equal to the original data frame.
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Since a logical vector is as long as the original variables, the new variable is a good match, so we'll save it there. You can use the saved logical vector to select observations. Note that when we use a saved logical vector to select, it is not put in quotes. Since they're in quotes, they make up a character vector. This prints the first 4 cases selected by their row name. This assigns more useful row names. Note that this vector's length is not equal to the number of rows in the data frame, so it cannot be stored there.
Note that it is not enclosed in quotes when used this way. All the rules that work for rows also work for columns.
Forexample,printingvariablesgenderthroughq4forjust thefemalescouldbedonewithanyoftheseapproaches:. Withinthat,thereisonlyone structure,thevariable. R takesadvantageofthesebyhavingthesamefunction procedure dodifferentthingsdepending onwhatyougiveit. Sotocontrolafunctionyouhavetobeawareofwhattypeofobjectyoure givingit,thetypesofobjectsthefunctionisabletoaccept,whatitdoeswitheachandhowto convertfromonedatastructuretoanother. However,somefunctionswill indeedacceptthefirstform.
InthesectiononSelectingVariables,Isaidthatmydata[ ,3]andmydatawere almostthesame. Similarly,Isaidmydata[q1]andmydata[ ,q1]werealmostthe same. Butsomeproceduresare pickierthanothersandrequireveryspecificdatastructures. Thesecommandspassthedatain theformofadataframe mydata,mydata["q1"].
Thesepassthedataintheformofavector:mydata[ ,3],mydata[ ,"q1"]. An exceptiontothatisthatselectingacolumnusingtheform mydata[ ,3]willpassthedataas adataframewhileselectingarowusingthesametypeofnotation, mydata[3, ]passesthe dataasavector! Ifyouhavehavingaproblemfiguringoutwhichformofdatayouhave,therearefunctionsthat willtellyou. Forexample,class mydata willtellyouitsclassisdataframeand mode mydata willtellyoulist. Forexample, is.
ItismorelikeSPSS whereaslongasyouhavedatareadin,youcanmodifyit. Inotherwords,althoughRhasloops,theyarenotneededforthis typeofmanipulation. Thebasictransformationsincludesqrtforsquareroot,logfornatural logarithm,log10forthebase10logarithmandsoon. Asfortherightsideof theequation,youcanusethatmethodtoo,butitislonger:. Anotherwaytousetheshorternameswithoutattachinganddetachingiswiththetransform function.
Itistheequivalenttoattachingadataframe,performingasmanytransformationsas youlikeusingshortvariablenamesandthendetachingthedata. Youcanevenusetheshorter nameforminthecreatedvariable s. Thiswouldcreateavariable7where previouslywehadonly6. Ifyou'reusingtheindex approach,itisprobablyeasiertoinitializeanewvariablebybindinganewvariabletomydata. Thecolumnbindfunction,cbind,letsyounamethenewvariable,initializeittozeroandthen bindittomydata:. R Program for Transforming Variables.
If any is missing, the result is missing. The result will be missing only if all qs are missing. This selects the qs using the select function.
Rdata" Saves the R file. For example,theformulasforrecommendeddailyallowancesofvitaminsdifferformalesand females. R Program for Conditional transformations. Rdata" print mydata attach mydata Makes this the default dataset. It identifies the people who strongly agree with question 4. It identifies people who agree with question 4. The variable workshop1q4ge5 will be 1 when workshop 1 has q4 greater than or equal to 4, i. However, it specifies only the female condition, assuming male is true whenever female is false.
So if gender were missing, they would get the male code. However, it checks for the male gender so it will not assume missing genders are male. The nesting involved is quite a bit more complex than the example above.
If workshop or q4 are missing, it will use the second formula. ThelettersNAarealsoanobjectinR thatyoucanusetoassignmissingvalues.
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Whenimportingdata,blanksarereadasmissing whenblanksarenotusedasdelimiters asis thestringNA. Butifyouhaveothervalues,youwillofcoursehavetotellRwhichvaluesare missing. Forexamplea2columnvariablesuchasyearsofeducationmayhave99representmissing,but thevariableagemayhave99asavalidvalue. PeriodsthatrepresentmissingvaluesinSAScauseRtoreadthewholevariableasacharacter vector. Soyouhavetofirstfixthemissingvaluesandthenconvertittonumericusingthe as.
Soifyouwantedtosubstituteanothervaluesuchasthemean, youwouldneedtousetheis. NA is the missing value code in R.
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There are no nines in the data, but you can put a few there in q1 manually in the data editor using fix mydata. The lapply function applies a function to every member of a list a data frame is a type of list. If you know their column numbers, use this approach.
We use the which function to find out the column. Ifyouhaveonlyoneformulatoapplytoeachsubgroup,readthesectionaboveon conditionaltransformations. Theexamplebelowshowshowtohandleasetofformulasforeach subgroup. NotethatIdonotuseattach mydata whichwouldallowmetorefertovariablesbytheir shortname,e.