Biostat Lab Section SAS functions

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Biostat Lab Section SAS functions

• Yu-Fen Li

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SAS functions

• When planning modifications to SAS datasets,
  examine the many SAS functions that are available
  
• SAS has many built in functions that greatly
  reduce the need to enter commands
• SAS functions are pre-written expressions that
  provide shortcuts for many calculations and
  manipulations of data

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SAS Operators

• Operators
• comparison operator lt, gt, and
• addition (), subtraction (-), division (/), and
  multiplication ()
• meanscore (score1 score2) / 2
• A missing value is assigned if any argument is
  missing
• concatenation operator
• idnum schcode id

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Some Arithmetic Functions

• SQRT - calculates the square root
• newx SQRT(x)
• LOG/LOG2/LOG10 - calculates the logarithm to the
  base e/2/10
• newx LOG (x)
• ABS - returns the absolute value
• newx ABS (x)
• MOD - calculates the remainder
• newx MOD (x,3)

x4 gt newx2
x4 gt newx1.3863
x-4 gt newx4
x4 gt newx1
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Some Sample Statistic Functions

• MEAN - computes the arithmetic mean (average)
• meanz MEAN (4,9,3,8,.)
• CV - calculates the coefficient of variation
• MAX - returns the largest value
• MIN - returns the smallest value
• N - returns the number of nonmissing arguments
• NMISS - returns the number of missing arguments
• RANGE - calculates the range
• STD - calculates the standard deviation
• STDERR - calculates the standard error of the
  mean
• SUM - calculates the sum of the arguments

WHAT is your answer?
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Some Truncation Functions
x4.972

• CEIL - returns the smallest integer greater than
  or equal to the argument
• newx CEIL (x)
• FLOOR - returns the largest integer less than or
  equal to the argument
• newx FLOOR (x)
• INT - returns the integer value
• newx INT (x)
• ROUND - rounds a value to the nearest round-off
  unit
• newx1 ROUND (x, 0.01)
• newx2 ROUND (x, 0.1)

newx5
newx4
newx4
newx14.97
newx25
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Some Character Functions
XaBC.DdF(Xy)

• SCAN - scans for words
• newx SCAN (x,2,.)
• SUBSTR - extracts a substring
• newx SUBSTR (x,3,2)
• TRIM - removes trailing blanks
• newx TRIM (x)
• LOWCASE - converts all to lowercase
• newx LOWCASE (x)
• UPCASE - converts to uppercase
• newx UPCASE (x)

DdF(Xy)
C.
aBC.DdF(Xy)
abc.ddf(xy)
ABC.DDF(XY)
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Some Date and Time Functions

• MDY - returns a SAS date value from month, day,
  and year
• For example, MDY(10,17,91) returns the SAS date
  value '17OCT91'D
• DAY - returns the day of the month from a SAS
  date value
• DAY ('17OCT91'D) give a number 17
• MONTH - returns the month from a SAS date value
  or literal
• MONTH ('17OCT91'D) give a number 10
• YEAR - returns the year from a SAS date value
• YEAR ('17OCT91'D) give a 4-digit number 1991

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In-Class Assignment

• Generate the following data in SAS
• Calculate the mean score of 3 tests for each
  student
• a missing score is counted as a test of score 0

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In-Class Assignment

• Calculate the age for all students
• Age round up (REF dob)/365.25 to a integer
• REF is set as 1/1/2008
• List the mean score for students whose name
  starts with a J
• List the mean score for students whose birth year
  was in 80s