What syntax can be used to create case selection/verification/recode conditions (or to calculate variable values using spreadsheet formulas)?
Recoding variable values, performing case selection for analyses, or verifying quality of data involve a comparison of conditions or values encountered in the spreadsheet with conditions specified by an expression to determine a further action for each case (that is, respectively assigning a new variable value, including the case in an analysis, or verifying that the data associated with a case are correct). Assigning variable values using a spreadsheet formula involves case-by-case calculation of values for a variable based directly on the values of other spreadsheet variables and parameters not included in the spreadsheet. For data transformations more extensive or more complex than can be accomplished using the variable recode and spreadsheet formula facilities provided, use the Statistica Visual Basic language.
Follow these guidelines to create case selection, verification, or recode conditions.
- Refer to variables by either their numbers (example, v1 = 1) or their names (example, Gender = 1). Note that you can type variable names in either upper case or lower case letters (that is, "GENDER" is equivalent to "gender"). Note also that v0 refers to the case number when used in expressions.
- In expressions, enclose text labels of a variable in single quotation marks (example, v1 = 'MALE'). Note that you can type text labels in either upper case or lower case letters (that is, 'YES' is equivalent to 'yes').
- In expressions or spreadsheet formulas, enclose variable names containing special characters (example, spaces, plus or minus signs) in single quotation marks. If the single quotation mark itself occurs in the variable name, use double quotation marks instead (example, "A's Score"). Note that if double quotation marks are used in the name, then the variable name must be placed in single quotation marks.
- Syntax conversions for spreadsheet formulas
- Spreadsheet formulas (specified on the Variable specifications dialog accessed by the Data - Variable Specs menu) must start with an equal sign. When you enter a label that starts with an equal sign, Statistica assumes that it is a formula and verifies it for formal correctness. Note that a semicolon after a formula starts a comment: example, = v1 + v2; this is a comment.
- Missing values
- The IsMD(x) function returns a value of true (1) if the passed expression is a missing data value. For additional details on how missing values are treated in the evaluation of logical and arithmetic expressions, see Logical and Arithmetic Expressions Involving Missing Data Values Always Evaluate to FALSE or Missing Data.
- Operators
- A number of arithmetic, relational, and logical operators are available for creating expressions for recoding, case selection, and data verification or for creating spreadsheet formulas.
Arithmetic: +, -, *, /, ** or ^ (exponentiation), ( )
Relational:
= (equal to)
<>, >< (not equal to)
< (less than)
> (greater than)
<= (less than or equal to)
>= (greater than or equal to)
Logical:
AND (equivalent to &)
OR (equivalent to !)
NOT (equivalent to ~)
- Math functions
- Math functions can be used in expressions for recoding, case selection or data verification as well as in spreadsheet formulas for calculating variable values. If the value of any variable used in the expression or formula is missing (in the current case), then the expression evaluates to missing data (for the current case).
Abs(x) absolute value of x Arccos(x) arc cosine of x Arcsin(x) arc sine of x Arctan(x) arc tangent of x Cos(x) cosine of x hyperbolic cosine of x Exp(x) e to the power of x Hypot(x,y) returns hypotenuse of x and y (square root(x2 + y2)) Log(x) natural logarithm of x Log2(x) binary logarithm of x Log10(x) common logarithm of x Max(x,y) returns the greater of x and y Min(x,y) returns the lesser of x and y Rnd(x) random number in the range of 0 to x RndNormal(x) random number from a normal distribution with mu=0 and sigma=x RndPoisson(x) random number from a Poisson distribution with parameter x Sign(x) sign of x: if x>0 then +1, if x<0 then -1, if x = 0 remains 0 Sin(x) sine of x SinH(x) hyperbolic sine of x Sqrt(x) square root of x Tan(x) tangent of x TanH(x) hyperbolic tangent of x Trunc(x) truncate x to an integer "towards zero" Uniform(x) random value in range 0 to x (same as Rnd(x)) Function names are not case sensitive, that is, Log(x) is the same as log(x) or LOG(x). As indicated in the function list above, math functions accept one to two arguments depending on the function. The position of the function in the expression or spreadsheet formula is replaced by the return value of the function. Numeric values (example, Sqrt(155)), variable names (example, Max(SCORE1,SCORE9)), or variable numbers (example, Log(v8)) are acceptable arguments. Additional arguments acceptable to math functions are expressions that evaluate to a number (example, Max(v7,(v5+v8-BASELINEVALUE)/3)) or functions that return a numeric result (example, Sin(Sqrt(v5))). Some commonly used constants can also be specified in expressions and formulas by reference: example, Pi = 3.14... Euler (e) = 2.71...
- Statistics functions
- Nine statistics functions that accept lists of values and ranges and arguments, and adjust to missing data, are also available for use in recoding, case selection, and verification expressions as well as in spreadsheet formulas:
Mean(x1, x2,..xn) mean of n arguments Median(x1, x2,..xn) 50th percentile of n arguments Perc25(x1, x2,..xn) 25th percentile of n arguments Perc75(x1, x2,..xn) 75th percentile of n arguments Statmax(x1, x2,..xn) maximum of n arguments Statmin(x1, x2,..xn) minimum of n arguments Stdev(x1, x2,..xn) standard deviation of n arguments Sum(x1, x2,..xn) sum of n arguments Validn(x1, x2,..xn) number non-missing of n arguments Note: The Statmin and Statmax functions have the stat prefix to distinguish them from the arithmetical Max and Min (math) functions discussed above. Like math functions, the names of statistics functions are not case sensitive when used in expressions and formulas.All statistics functions ignore arguments that contain missing values, basing their results on non-missing data only. Unlike math functions, statistics functions do not evaluate to a missing result unless all arguments are missing values or an argument is encountered that evaluates to an undefined value (example, square root of a negative number or division by zero). Also unlike math functions, each statistics function accepts any number of arguments placed in parentheses and separated by commas.
The following are acceptable statistics function arguments:
Numbers example, Mean(18,80,120,68,40) Variable names example, Mean(SALARY,1050,BONUS,500) Variable numbers example, Stdev(120,v3,v2,v8,255) Ranges of variables designated by name or number (use colons to define ranges) example, Sum(v54,COST1:COST5,2550,v23:v35,1575,OVERHEAD) Expressions that evaluate to a number example, Mean(500,(v6+456)/v3),TRAVELEXPENSE,v8) Functions that return a numeric result example, Mean(220,Sqrt(v8+v7),v12) - Distribution functions and their integrals
- Statistica provides a predefined broad selection of distribution functions, their integrals and inverse distribution functions that can be used in spreadsheet formulas and in recoding, case selection, and verification expressions like all other functions.
Below is a listing of all available distributions (parameters are given in parentheses):
Distribution Density/ Probability Function Distribution Function Inverse Distribution Function Beta beta(x,n,w) ibeta(x,n,w) vbeta(x,n,w) Binomial binom(x,p,n) ibinom(x,p,n) Cauchy cauchy(x,h,q) icauchy(x,h,q) vcauchy(x,h,q) Chi-square chi2(x,n) ichi2(x,n) vchi2(x,n) Exponential expon(x,l) iexpon(x,l) vexpon(x,l) Extreme extreme(x,a,b) iextreme(x,a,b) vextreme(x,a,b) F F(x,n,w) iF(x,n,w) vF(x,n,w) Gamma gamma(x,c) igamma(x,c) vgamma(x,c) Geometric geom(x,p) igeom(x,p) Laplace laplace(x,a,b) ilaplace(x,a,b) vlaplace(x,a,b) Logistic logis(x,a,b) ilogis(x,a,b) vlogis(x,a,b) Lognormal lognorm(x,m,s) ilognorm(x,m,s) vlognorm(x,m,s) Normal normal(x,m,s) inormal(x,m,s) vnormal(x,m,s) Pareto pareto(x,c) ipareto(x,c) vpareto(x,c) Poisson poisson(x,l) ipoisson(x,l) Rayleigh rayleigh(x,b) irayleigh(x,b) vrayleigh(x,b) Student's t student(x,df) istudent(x,df) vstudent(x,df) Weibull weibull(x,b,c,q) iweibull(x,b,c,q) vweibull(x,b,c,q)