Case Selection Conditions - Syntax Summary
Recoding variable values, performing case selection for analyses, or verifying quality of data involves 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 by 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 Statistica Visual Basic.
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 (i.e., "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.
Using a case selection condition such as "v2='MALE'" with the above data set selects only the last case. This is because the variable MALE takes precedence over the variable GENDER's text label. If you intend to case select on a variable's text labels, but a conflict with another variable's name arises, place a '$' at the end of the expression. For example, "v2='MALE'$" yields the following result:
Syntax conversions for spreadsheet formulas
Spreadsheet formulas (specified in the Variable specifications dialog box accessed by selecting Variable Specs on the Data 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 details on how missing data values are handled in arithmetic and logical expressions (example, in case selection conditions, spreadsheet formulas), 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 |
| CosH(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, i.e., 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 will be replaced by the return value of the function. Numeric values [e.g., Sqrt(155)], variable names [e.g., Max(SCORE1,SCORE9)], or variable numbers [e.g., Log(v8)] are acceptable arguments. Additional arguments acceptable to math functions are expressions that evaluate to a number [e.g., Max(v7,(v5+v8-BASELINEVALUE)/3)] or functions that return a numeric result [e.g., Sin(Sqrt(v5))]. Some commonly used constants can also be specified in expressions and formulas by reference: e.g., Pi = 3.14... Euler (e) = 2.71...
Statistics functions
Nine statistics functions that accept lists of values and/or 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 |
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.
For a listing of available distributions see Spreadsheet Formulas - Distributions and Their Functions.
Selection Using Dates
Statistica can select cases based on dates by enclosing the date with # symbols. For example, if you want to select the week of January 18 through 24, 2009, for variable 6, the case selection condition is: v6>=#1/18/2009# AND v6<=#1/24/2009#. Time functions can also be used with this selection method, for example: v6 > #3/5/07 12:03AM#.
For transformations of text variables (variables of type text), see also, Transformation of Text Variables (Variables of Type Text). Note that Statistica Spreadsheets also support text labels for numeric values (these are labels attached to numeric values and are used for display purposes only); when transforming the values with attached text labels, the respective transformations are performed on the numeric representations and not on the text labels.