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Working With Dates: Dates Come in Many Ways

Working With Dates: Dates Come in Many Ways. 10/18/04 18/10/04 10/18/2004 18OCT2004 101804 October 18, 2004 Need to know how to read-in dates and then work with them. What do you want to do with dates?. Display them Compare two dates: find the number of days between 2 dates

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Working With Dates: Dates Come in Many Ways

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  1. Working With Dates:Dates Come in Many Ways • 10/18/04 • 18/10/04 • 10/18/2004 • 18OCT2004 • 101804 • October 18, 2004 Need to know how to read-in dates and then work with them

  2. What do you want to do with dates? • Display them • Compare two dates: find the number of days between 2 dates ndays = date2 - date1;Will this work?

  3. DATA dates; INFILE DATALINES; INPUT @1 brthdate mmddyy10.; * Use informat; DATALINES; 03/03/1971 02/14/1956 01/01/1960 ; PROCPRINT; VAR brthdate; PROCPRINT; VAR brthdate; FORMAT brthdate mmddyy10.; ------------------------------------------------------ Obs brthdate 1 4079 2 -1417 3 0 Obs brthdate 1 03/03/1971 2 02/14/1956 3 01/01/1960 Jan 1, 1960

  4. When you read in a variable with a date informat: • SAS makes the variable numeric • SAS assigns the numeric value relative to January 1, 1960 • This makes it easy to subtract two dates to get the number of days between the dates. • dayselapsed = date2 – date1;

  5. * Program 8 ; DATA age; INFILE‘C:\SAS_Files\tomhs.data' ; INPUT @14 randdate mmddyy10. @34 brthdate mmddyy10. ; agedays = randdate - brthdate ; ageyrs = (randdate - brthdate)/365.25; ageint = INT( (randdate - brthdate)/365.25); yrrand = YEAR(randdate);

  6. PROCPRINTDATA=age (obs=5); VAR brthdate randdate agedays ageyrs ageint ; TITLE'Printing Dates Without a Date Format'; RUN; PROCPRINTDATA=age (obs=5); VAR brthdate randdate agedays ageyrs ageint ; FORMAT brthdate mmddyy10. randdate mmddyy10.; TITLE'Printing Dates With a Date Format'; RUN;

  7. Printing Dates Without a Date Format Obs brthdate randdate agedays ageyrs ageyrsX ageint 1 -8589 10175 18764 51.3730 51.3739 51 2 -6880 10239 17119 46.8693 46.8711 46 3 -12572 10002 22574 61.8042 61.8055 61 4 -9592 10175 19767 54.1191 54.1205 54 5 -12996 10280 23276 63.7262 63.7268 63 All before 1960

  8. Printing Dates With a Date Format Obs brthdate randdate 1 06/26/1936 11/10/1987 2 03/01/1941 01/13/1988 3 07/31/1925 05/21/1987 4 09/27/1933 11/10/1987 5 06/02/1924 02/23/1988

  9. PROCFREQDATA=age; TABLES yrrand ; TITLE'Frequency Distribution of Year Randomized'; RUN; The FREQ Procedure Cumulative Cumulative yrrand Frequency Percent Frequency Percent ----------------------------------------------------------- 1986 9 9.00 9 9.00 1987 65 65.00 74 74.00 1988 26 26.00 100 100.00

  10. Topics • Reading SAS datasets • Sub-setting SAS datasets • Merging SAS datasets

  11. Working With SAS Data Sets • Reading SAS dataset • SET Statement • Merging SAS datasets • MERGE Statement Done within a DATA step

  12. SET STATEMENT • Reads SAS data set • Replaces INFILE and INPUT statements used when reading in raw data • KEEP brings in selected variables (columns) • Where brings in selected observations (rows) DATA new; SET old (KEEP = varlist); WHERE = condition; RUN; This creates a new data set called new that has the variables in varlist and selected observations from old.

  13. PROGRAM 9 Making SAS Datasets from Other SAS Datasets; DATA tdata; INFILE‘C:\SAS_Files\tomhs.data' ; INPUT @ 1 ptid $10. @ 12 clinic $1. @ 25 group 1. @ 30 sex 1. @ 123 sbp12 3. @ 14 randdate $10. ; RUN; * Making a new dataset containing only men; DATA men; SET tdata; * reads the existing dataset; WHERE sex = 1; This does the selection; ifgroup in(1,2,3,4,5)thenactive = 1;else ifgroup in(6)thenactive = 2; KEEP ptid clinic group sbp12 randdate active; RUN;

  14. PROGRAM 10 - Merging SAS Datasets DATA clinic; INFILE DATALINES; INPUT id $ sbp ; DATALINES; C03615 115 B00979 107 B00644 138 D01348 142 A01088 117 B01408 121 B00025 130 B00714 144 A01166 113 … more data ; DATA lab; INFILE DATALINES; INPUT id $ glucose; DATALINES; C03615 102 B00644 089 D01348 111 A01088 093 B01408 094 B00025 077 B00714 100 A01166 113 D00942 103 … more data ;

  15. * Creating merged dataset; PROC SORT DATA= clinic; BY id; PROC SORT DATA= lab; BY id; DATA study; MERGE clinic lab; BY id ; RUN; Note: The BY statement is very important!

  16. Merged Dataset Obs id sbp glucose 1 A00869 110 99 2 A01088 117 93 3 A01166 113 113 4 B00025 130 77 5 B00644 138 89 6 B00714 144 100 7 B00867 114 98 8 B00979 107 . 18 D00942 . 103 20 D01809 129 .

  17. Things to Remember When Merging Datasets • Need to have common variable name is each dataset to use as linking variable • Variables in dataset with no match will be set to missing • Rows matched that have same variable names will be assigned right-most dataset value • Always remember the BY statement in the merge!

  18. Temporary vs Permanent SAS Datasets Temporary (or work) SAS dataset - After SAS session is over the dataset is deleted. DATA bp; * bp is deleted after SAS session; Permanent SAS dataset - After program is run the dataset is saved and is available for use in future programs. You need to tell SAS where to store/retrieve the dataset. Note: For PC SAS the work dataset is available until you end the SAS session.

  19. Reasons to Create Permanent SAS Datasets • Read raw data and compute calculated variables only once • All variables have assigned names and labels. • Data is ready to be analyzed. • Dataset can be sent to other computers or users.

  20. Creating a Permanent Dataset LIBNAMEmylib‘C:\My SAS Datasets’; LIBNAME – assigns a directory (folder) reference name. In this example the directory ‘C:\My SAS Datasets’ is assigned a reference name of mylib. DATAmylib.sescore; Tells SAS to create a dataset called sescore in the directory referenced by mylib, which is ‘C:\My SAS Datasets’.

  21. PROGRAM 11 LIBNAMEmylib‘C:\SAS_Files'; DATAmylib.sescore; INFILE‘C:\SAS_Files\tomhs.data'LRECL =400; INPUT @ 1 ptid $10. @ 12 clinic $1. @ 14 randdate mmddyy10. @ 25 group 1. @ 49 educ 1. @ 85 wtbl 5.1 @ 97 wt12 5.1 @115 sbpbl 3.0 @123 sbp12 3.0 @236 (sebl_1-sebl_20) (1. +1) @276 (se12_1-se12_20) (1. +1) ;

  22. wtd12 = wt12 - wtbl; sbpd12 = sbp12 - sbpbl; sescrbl = MEAN (OF sebl_1 - sebl_20) ; sescr12 = MEAN (OF se12_1 - se12_20) ; sescrd12 = sescr12 - sescrbl ; LABEL educ = 'Highest Education Level'; LABEL wt12 = 'Weight (lbs) at 12 Months'; LABEL wtbl = 'Weight (lbs) at Baseline'; LABEL wtd12 = 'Weight Change at Baseline'; LABEL sbpbl = 'Systolic BP (mmHg) at Baseline'; LABEL sbp12 = 'Systolic BP (mmHg) at 12 Months'; LABEL sbpd12 = 'Systolic BP Change at 12 Months'; LABEL group = 'Treatment Group (1-6)'; LABEL sescrbl = 'Side Effect at Baseline'; LABEL sescr12 = 'Side Effect at 12 Months'; LABEL sescrd12 = 'Side Effect Change Score'; FORMAT randdate mmddyy10. ; DROP sebl_1-sebl_20 se12_1-se12_20 ;

  23. 60 LIBNAME mylib 'C:\SAS_Files'; NOTE: Libref MYLIB was successfully assigned as follows: Engine: V9 Physical Name: C:\SAS_Files DATA mylib.sescore; NOTE: The infile 'C:\SAS_Files\tomhs.data' is: File Name=C:\SAS_Files\tomhs.data, RECFM=V,LRECL=400 NOTE: 100 records were read from the infile 'C:\SAS_Files\tomhs.data'. NOTE: The data set MYLIB.SESCORE has 100 observations and 14 variables.

  24. Using PROC COPY to copy work dataset to permanent dataset Make a work dataset first – then when you know that is working correctly copy the work dataset to a permanent dataset. LIBNAMEmylib‘C:\SAS_Files'; DATA sescore; …. RUN; PROC COPY IN=work OUT=mylib; SELECT sescore; RUN;

  25. Reading Permanent SAS Dataset LIBNAMEclass‘C:\SAS_Files' ; * Tells SAS where to find the SAS dataset; PROCMEANSDATA=class.sescore ; TITLE'Means of All Numeric Variables on SAS Permanent Dataset'; RUN; What if dataset was moved to a different folder? Just need to change LIBNAME

  26. *---------------------------------------------------------------**---------------------------------------------------------------* Often you will read the permanent SAS dataset in a DATA step to modify or add variables. Usually these will be put on a new work SAS dataset. *---------------------------------------------------------------*; LIBNAME class 'C:\SAS_Files' DATA rxdata; SET class.sescore; if group in(1,2,3,4,5) then rx = 1; else rx = 2; RUN; PROCMEANSDATA=rxdata NMEANMAXDEC=2FW=7; CLASS group; VAR sbpd12 wtd12 sescrd12; TITLE'Change in SBP, Weight, and Side Effect Score by Treatment'; RUN;

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