SAS 101. Based on Learning SAS by Example: A Programmer s Guide Chapters 9, 11 & 12. By Tasha Chapman, Oregon Health Authority

Transcription

1 SAS 101 Based on Learning SAS by Example: A Programmer s Guide Chapters 9, 11 & 12 By Tasha Chapman, Oregon Health Authority

2 Topics covered SAS dates Date functions Numeric functions Character functions Special functions PUT and INPUT

3 SAS dates

4 SAS dates Dates are stored as the number of days from January 1 st, 1960 Dates before 1960 are negative numbers Dates after 1960 are positive numbers Examples: 1/1/1960 = 0 1/2/1960 = 1 10/21/1950 = -3,359 12/31/2012 = 19,358

5 SAS dates Times are stored as the number of seconds from midnight Times are always positive Examples: Midnight = 0 Midnight and 36 seconds = 36 5:38am and 9 seconds= 20,289 12:51pm and 2 seconds = 46,262

6 SAS dates Datetime values are stored as the number of seconds from 1/1/1960 Datetimes before 1960 are negative numbers Datetimes after 1960 are positive numbers Examples: 1/1/1960 at midnight and 36 seconds = 36 1/2/1960 at 5:38am and 9 seconds = 106,689 10/21/1950 at 12:51pm & 2 secs = -290,171,338 12/31/2012 at midnight = 1,672,531,200

7 Common date formats/informats If you input 14686: Format Result MMDDYY10. 03/17/2000 MMDDYY8. 03/17/00 MONNAME. March YEAR MONYY. MAR2000 WORDDATE. March 17, 2000 WEEKDATE. Friday, March 17, 2000 DOWNAME. Friday QTR. 1 YYQ. 2000Q1

8 Common date formats/informats If you input 14686: Format Result MMDDYY10. 03/17/2000 MMDDYY8. 03/17/00 MONNAME. March YEAR MONYY. MAR2000 WORDDATE. March 17, 2000 WEEKDATE. Friday, March 17, 2000 DOWNAME. Friday QTR. 1 YYQ. 2000Q1

9 Examples of date formats SAS Documentation

10 Using dates Date constants can be used in IF and WHERE statements, functions, and other portions of your SAS code These are written as: 'DDMONCCYY'd

11 Using dates The current date can be computed using the TODAY() function

12 Using dates Datetime constants can be also be used in your SAS code These are written as: 'DDMONCCYY:HH:MM:SS'dt

13 Using dates BEWARE! If your database stores datetime variables 1,441,193,037 '30sep2005:11:23:57'dt is the not same thing as '30sep2005'd 16,709 30sep2005:00:00:00 dt

14 Using dates BEWARE! If your database stores datetime variables '01sep2005'd le mod_date le '30sep2005'd may ignore datetime values on September 30 th with non-zero times

15 Using dates BEWARE! If your database stores datetime variables Alternatives: '01sep2005:00:00:00'dt le mod_date le '30sep2005:23:59:59'dt

16 Using dates BEWARE! If your database stores datetime variables Alternatives: '01sep2005'd le mod_date lt '01oct2005'd * This option does not work with a SAS dataset

17 Reading dates from raw data Informat works fine if you know the format of the incoming data and the data is consistent but what if the data is wonky?

18 Reading dates from raw data Dates come in all shapes and sizes, sometimes even in the same data file How do we deal with them all?

19 Reading dates from raw data Use anydtdte. informat to deal with wonky date data.

20 Reading dates from raw data Informat anydtdte. anydtdtm. anydttme. Purpose Extracts the date portion Extracts the datetime portion Extracts the time portion

21 Reading dates from raw data When reading a two-digit year, SAS uses a 100- year interval to determine which century the year belongs to Default is 1920 Use yearcutoff= system option to change default

22 Reading dates from raw data

23 Reading dates from raw data

24 Functions

25 What are functions? function(argument-1, argument-2) Functions return a value from a computation or system manipulation based on supplied arguments Arguments can be constants, variables, or expressions, depending on the function Can nest functions within functions Most often use functions to create new variables or as part of conditional logic

26 Functions vs. PROCs Functions vs. PROCs Functions calculate across variables (one value per observation) PROCs calculate down observations (one value per dataset) Would provide a single score per student that averages all of his/her test scores Would provide an average score for all students for test 1 Graphic from Introduction to SAS Functions by Neil Howard

27 Examples of functions SAS Documentation

28 Date functions

29 Date functions

30 Date functions Function Purpose Sample Output datepart(datetime); Extract date portion from a datetime value timepart(datetime); Extract time portion from a datetime value year(date); Extract year from a date value 2009 month(date); Extract month from a date value 12 day(date); Extract day of the month from a date value 31 weekday(date); Extract day of the week from a date value 2 mdy(month, day, year); Create a date using month, day and year values 17905

31 Date functions Function Purpose Sample Output datepart(datetime); Extract date portion from a datetime value timepart(datetime); Extract time portion from a datetime value year(date); Extract year from a date value 2009 month(date); Extract month from a date value 12 day(date); Extract day of the month from a date value 31 weekday(date); Extract day of the week from a date value 2 mdy(month, day, year); Create a date using month, day and year values 17905

32 Date functions Many uses of functions

33 INTCK function INTCK(interval, from, to) Returns a count of the number of interval boundaries between two dates, times, or datetime values interval : desired interval Examples: 'YEAR' 'MONTH' 'DAY' 'QTR' from : Starting date, time, or datetime value to : Ending date, time, or datetime value

34 INTCK function Interval counted each time a boundary is crossed Interval Boundary 'YEAR' January 1 'MONTH' 'DAY' First of any month Start of each day 'QTR' January 1, April 1, July 1, and October 1

35 INTCK function Examples of INTCK Function Result intck('day', '01jan2013'd, '01jan2013'd) 0 intck('day', '01jan2013'd, '02jan2013'd) 1 intck('year', '01jan2013'd, '01apr2013'd) 0 intck('year', '01dec2012'd, '01apr2013'd) 1 intck('year', '01jan2013'd, '01apr2014'd) 1

36 INTCK function Examples of INTCK Function Result intck('day', '01jan2013'd, '01jan2013'd) 0 intck('day', '01jan2013'd, '02jan2013'd) 1 intck('year', '01jan2013'd, '01apr2013'd) 0 intck('year', '01dec2012'd, '01apr2013'd) 1 intck('year', '01jan2013'd, '01apr2014'd) 1

37 INTCK function Can use INTCK function to classify observations

38 Frequency of admissions INTCK function 1200 Hospital Admissions by Quarter January 1, 2003 through June 30, Calendar quarter

39 Calculating age Different methods produce different results Most commonly recognized

40 INTNX function INTNX(interval, from, n, <alignment>) Increments a date, time, or dateime value by a given interval interval : desired interval from : Starting date, time, or datetime value n : number of interval increments Can be positive, negative, or zero alignment : optional argument that controls the alignment of the date 'SAMEDAY', 'BEGINNING', 'MIDDLE', or 'END Default is 'BEGINNING'

41 INTNX function Examples of INTNX Function Result intnx('day', '01jan2013'd, 3) 01/04/2013 intnx('year', '25jan2013'd, 1) 01/01/2014 intnx('year', '30aug2012'd, -31) 01/01/1981 intnx('year', '30aug2012'd, -31, 'SAMEDAY') 08/30/1981

42 INTNX function Examples of INTNX Function Result intnx('day', '01jan2013'd, 3) 01/04/2013 intnx('year', '25jan2013'd, 1) 01/01/2014 intnx('year', '30aug2012'd, -31) 01/01/1981 intnx('year', '30aug2012'd, -31, 'SAMEDAY') 08/30/1981

43 INTNX function Can use INTNX function to help automate reports

44 Numeric functions

45 ROUND function ROUND(argument, <rounding-unit>) Rounds a number to the selected rounding unit argument : numeric value to be rounded rounding-unit : optional increment for rounding Default is 1 (nearest integer) Function Result round( , 1) 157 round( , 10) 160 round( ,.01)

46 INT function INT(argument) Truncates argument to an integer value (drops the decimal point) argument : numeric value to be truncated Function Result int( ) 156

47 Descriptive stats functions Two methods: function(var1, var2, varn) function(of var1-varn) Can use these methods separately or together Function (example) N(Q1, Q2, Q3, Q4) Mean(of Q1-Q4) Sum(0, of Q1-Q4) Min(of Q1-Q4) Max(of Q1-Q4) Result Returns the number of non-missing numeric values Returns the arithmetic mean (average) Returns the sum of nonmissing values (in this example, if all arguments are missing, returns 0) Returns the smallest value Returns the largest value

48 RANUNI function RANUNI(seed) Generates a random number between 0 and 1 seed : a number which is used to generate the first number in the random sequence Can be any number If you use a seed of 0 or negative number, SAS will use the system clock to supply the seed Function ranuni( ) Result Returns a random number

49 LAG function LAG<n>(argument) Return value from a previous observation (generally) n : specifies the number of lagged values argument : number, expression or variable to be lagged

50 LAG function DIF function similar to LAG Returns the difference between current value and previous value i.e. DIF(x) = x lag(x)

51 LAG function

52 Character functions

53 CASE functions Converts character string to upper or lower case Function (example) upcase('sas rocks') lowcase('i AM WHISPERING') Result SAS ROCKS i am whispering Useful when using comparison operators

54 PROPCASE function PROPCASE(argument, <delimiters>) Converts all words to proper case argument : character value that will be converted delimiters : specifies one or more delimiters that indicate the beginning of a new word Enclose delimiters in quotation marks Default delimiters are blank, forward slash, hyphen, open parenthesis, period, and tab Use of option overrides all default delimiters Function propcase('saint KITTS/NEVIS(U.S.)') propcase("george O'KEEFE-BAIN", " '-"); Result Saint Kitts/Nevis(U.S.) George O Keefe-Bain

55 SUBSTR function SUBSTR(string, position, <length>) Extracts a substring (portion) of text string : character value that text will be extracted from position : beginning character position for substring length : length of substring to extract If omitted, SAS extracts the remainder of the string Function Result substr('jeff STREET', 5) STREET substr('621110', 1, 2) 62 substr('dr. Paul Jones', 5, 4) Paul

56 SCAN function SCAN(string, count, <charlist, <mods>>) Returns the nth word from a character string string : character value that words will be pulled from count : integer that specifies the number of the word to select Positive counts from left to right Negative counts from right to left charlist : optional delimiter identifier modifiers : optional modifier that changes the behavior of the SCAN function Function scan('jeff STREET', 2) Result STREET

57 CAT function Function cat('john', 'Smith') CAT(item1, item2, itemn) Concatenates items into a single character string items : value to be concatenated If numeric, value is first converted to character Can also be written as: CAT(of item1-itemn) cat('i', ' ', 'Heart', ' ', 'You') Result JohnSmith I Heart You cat('(', area, ')', prefix, '-', suffix) (503) cat(1225, ' Ferry St.') 1225 Ferry St.

58 COMPRESS function COMPRESS(<source>, <chars>, <modifiers>) Removes specified characters from a string source : character value from which characters will be removed chars : characters to be removed If omitted, only blanks will be removed modifiers : optional modifier that changes the behavior of the COMPRESS function Function( Result compress('mc Cartney') McCartney compress('(503) ', '()- ')

59 Special functions PUT and INPUT

60 PUT function PUT(source, format.) Returns a value using a specified format Most often used for converting numeric data to character source : value to be reformatted format : the format to be applied The format must be the same type as the source (character/numeric) Function Result put(patient_id, 8.) A patient ID that is character put(32000, dollar24.) $32,000 put(16739, date9.) put('m', $gender.) 30OCT2005 Male

61 PUT function PUT function vs. Format statements: Format statements change the appearance of the value PUT functions change the value itself Date and Char_Date look the same, but one is character and the other is numeric.

62 INPUT function INPUT(source, <???> informat.) Converts a value using a specified informat Most often used for converting character data to numeric source : value to be reformatted??? : Optional modifiers that suppress error messages informat : the informat to be applied Function Result input('32000', 5.) input('32000', 5.2) input('$ ', dollar24.2) input('30oct2005', date9.) 16739

63 For next week Read chapters 14 & 19