1 @node Data Manipulation, Data Selection, Variable Attributes, Top
2 @chapter Data transformations
3 @cindex transformations
5 The PSPP procedures examined in this chapter manipulate data and
6 prepare the active file for later analyses. They do not produce output,
10 * AGGREGATE:: Summarize multiple cases into a single case.
11 * AUTORECODE:: Automatic recoding of variables.
12 * COMPUTE:: Assigning a variable a calculated value.
13 * COUNT:: Counting variables with particular values.
14 * FLIP:: Exchange variables with cases.
15 * IF:: Conditionally assigning a calculated value.
16 * RECODE:: Mapping values from one set to another.
17 * SORT CASES:: Sort the active file.
20 @node AGGREGATE, AUTORECODE, Data Manipulation, Data Manipulation
26 OUTFILE=@{*,'filename'@}
31 /dest_var['label']@dots{}=agr_func(src_vars, args@dots{})@dots{}
34 @cmd{AGGREGATE} summarizes groups of cases into single cases.
35 Cases are divided into groups that have the same values for one or more
36 variables called @dfn{break variables}. Several functions are available
37 for summarizing case contents.
39 The OUTFILE subcommand is required and must appear first. Specify a
40 system file by file name string or file handle (@pxref{FILE HANDLE}).
41 The aggregated cases are written to this file. If @samp{*} is
42 specified, then the aggregated cases replace the active file.
44 By default, the active file will be sorted based on the break variables
45 before aggregation takes place. If the active file is already sorted
46 or otherwise grouped in terms of the break variables, specify
47 PRESORTED to save time.
49 Specify DOCUMENT to copy the documents from the active file into the
50 aggregate file (@pxref{DOCUMENT}). Otherwise, the aggregate file will
51 not contain any documents, even if the aggregate file replaces the
54 Normally, only a single case (for SD and SD., two cases) need be
55 non-missing in each group for the aggregate variable to be
56 non-missing. Specifying /MISSING=COLUMNWISE inverts this behavior, so
57 that the aggregate variable becomes missing if any aggregated value is
60 If PRESORTED, DOCUMENT, or MISSING are specified, they must appear
61 between OUTFILE and BREAK.
63 At least one break variable must be specified on BREAK, a
64 required subcommand. The values of these variables are used to divide
65 the active file into groups to be summarized. In addition, at least
66 one @var{dest_var} must be specified.
68 One or more sets of aggregation variables must be specified. Each set
69 comprises a list of aggregation variables, an equals sign (@samp{=}),
70 the name of an aggregation function (see the list below), and a list
71 of source variables in parentheses. Some aggregation functions expect
72 additional arguments following the source variable names.
74 Aggregation variables typically are created with no variable label,
75 value labels, or missing values. Their default print and write
76 formats depend on the aggregation function used, with details given in
77 the table below. A variable label for an aggregation variable may be
78 specified just after the variable's name in the aggregation variable
81 Each set must have exactly as many source variables as aggregation
82 variables. Each aggregation variable receives the results of applying
83 the specified aggregation function to the corresponding source
84 variable. The MEAN, SD, and SUM aggregation functions may only be
85 applied to numeric variables. All the rest may be applied to numeric
86 and short and long string variables.
88 The available aggregation functions are as follows:
91 @item FGT(var_name, value)
92 Fraction of values greater than the specified constant. The default
95 @item FIN(var_name, low, high)
96 Fraction of values within the specified inclusive range of constants.
97 The default format is F5.3.
99 @item FLT(var_name, value)
100 Fraction of values less than the specified constant. The default
103 @item FIRST(var_name)
104 First non-missing value in break group. The aggregation variable
105 receives the complete dictionary information from the source variable.
106 The sort performed by AGGREGATE (and by SORT CASES) is stable, so that
107 the first case with particular values for the break variables before
108 sorting will also be the first case in that break group after sorting.
110 @item FOUT(var_name, low, high)
111 Fraction of values strictly outside the specified range of constants.
112 The default format is F5.3.
115 Last non-missing value in break group. The aggregation variable
116 receives the complete dictionary information from the source variable.
117 The sort performed by AGGREGATE (and by SORT CASES) is stable, so that
118 the last case with particular values for the break variables before
119 sorting will also be the last case in that break group after sorting.
122 Maximum value. The aggregation variable receives the complete
123 dictionary information from the source variable.
126 Arithmetic mean. Limited to numeric values. The default format is
130 Minimum value. The aggregation variable receives the complete
131 dictionary information from the source variable.
134 Number of non-missing values. The default format is F7.0 if weighting
135 is not enabled, F8.2 if it is (@pxref{WEIGHT}).
138 Number of cases aggregated to form this group. The default format is
139 F7.0 if weighting is not enabled, F8.2 if it is (@pxref{WEIGHT}).
141 @item NMISS(var_name)
142 Number of missing values. The default format is F7.0 if weighting is
143 not enabled, F8.2 if it is (@pxref{WEIGHT}).
146 Number of non-missing values. Each case is considered to have a weight
147 of 1, regardless of the current weighting variable (@pxref{WEIGHT}).
148 The default format is F7.0.
151 Number of cases aggregated to form this group. Each case is considered
152 to have a weight of 1, regardless of the current weighting variable.
153 The default format is F7.0.
155 @item NUMISS(var_name)
156 Number of missing values. Each case is considered to have a weight of
157 1, regardless of the current weighting variable. The default format is F7.0.
159 @item PGT(var_name, value)
160 Percentage between 0 and 100 of values greater than the specified
161 constant. The default format is F5.1.
163 @item PIN(var_name, low, high)
164 Percentage of values within the specified inclusive range of
165 constants. The default format is F5.1.
167 @item PLT(var_name, value)
168 Percentage of values less than the specified constant. The default
171 @item POUT(var_name, low, high)
172 Percentage of values strictly outside the specified range of
173 constants. The default format is F5.1.
176 Standard deviation of the mean. Limited to numeric values. The
177 default format is F8.2.
180 Sum. Limited to numeric values. The default format is F8.2.
183 Aggregation functions compare string values in terms of internal
184 character codes. On most modern computers, this is a form of ASCII.
186 The aggregation functions listed above exclude all user-missing values
187 from calculations. To include user-missing values, insert a period
188 (@samp{.}) at the end of the function name. (e.g.@: @samp{SUM.}).
189 (Be aware that specifying such a function as the last token on a line
190 will cause the period to be interpreted as the end of the command.)
192 @cmd{AGGREGATE} both ignores and cancels the current @cmd{SPLIT FILE}
193 settings (@pxref{SPLIT FILE}).
195 @node AUTORECODE, COMPUTE, AGGREGATE, Data Manipulation
200 AUTORECODE VARIABLES=src_vars INTO dest_vars
205 The @cmd{AUTORECODE} procedure considers the @var{n} values that a variable
206 takes on and maps them onto values 1@dots{}@var{n} on a new numeric
209 Subcommand VARIABLES is the only required subcommand and must come
210 first. Specify VARIABLES, an equals sign (@samp{=}), a list of source
211 variables, INTO, and a list of target variables. There must the same
212 number of source and target variables. The target variables must not
215 By default, increasing values of a source variable (for a string, this
216 is based on character code comparisons) are recoded to increasing values
217 of its target variable. To cause increasing values of a source variable
218 to be recoded to decreasing values of its target variable (@var{n} down
219 to 1), specify DESCENDING.
221 PRINT is currently ignored.
223 @cmd{AUTORECODE} is a procedure. It causes the data to be read.
225 @node COMPUTE, COUNT, AUTORECODE, Data Manipulation
230 COMPUTE variable = expression.
232 COMPUTE vector(index) = expression.
235 @cmd{COMPUTE} assigns the value of an expression to a target
236 variable. For each case, the expression is evaluated and its value
237 assigned to the target variable. Numeric and short and long string
238 variables may be assigned. When a string expression's width differs
239 from the target variable's width, the string result of the expression
240 is truncated or padded with spaces on the right as necessary. The
241 expression and variable types must match.
243 For numeric variables only, the target variable need not already
244 exist. Numeric variables created by @cmd{COMPUTE} are assigned an
245 @code{F8.2} output format. String variables must be declared before
246 they can be used as targets for @cmd{COMPUTE}.
248 The target variable may be specified as an element of a vector
249 (@pxref{VECTOR}). In this case, a vector index expression must be
250 specified in parentheses following the vector name. The index
251 expression must evaluate to a numeric value that, after rounding down
252 to the nearest integer, is a valid index for the named vector.
254 Using @cmd{COMPUTE} to assign to a variable specified on @cmd{LEAVE}
255 (@pxref{LEAVE}) resets the variable's left state. Therefore,
256 @code{LEAVE} should be specified following @cmd{COMPUTE}, not before.
258 @cmd{COMPUTE} is a transformation. It does not cause the active file to be
261 When @cmd{COMPUTE} is specified following @cmd{TEMPORARY}
262 (@pxref{TEMPORARY}), the @cmd{LAG} function may not be used
265 @node COUNT, FLIP, COMPUTE, Data Manipulation
270 COUNT var_name = var@dots{} (value@dots{}).
272 Each value takes one of the following forms:
278 In addition, num1 and num2 can be LO or LOWEST, or HI or HIGHEST,
282 @cmd{COUNT} creates or replaces a numeric @dfn{target} variable that
283 counts the occurrence of a @dfn{criterion} value or set of values over
284 one or more @dfn{test} variables for each case.
286 The target variable values are always nonnegative integers. They are
287 never missing. The target variable is assigned an F8.2 output format.
288 @xref{Input/Output Formats}. Any variables, including long and short
289 string variables, may be test variables.
291 User-missing values of test variables are treated just like any other
292 values. They are @strong{not} treated as system-missing values.
293 User-missing values that are criterion values or inside ranges of
294 criterion values are counted as any other values. However (for numeric
295 variables), keyword MISSING may be used to refer to all system-
296 and user-missing values.
298 @cmd{COUNT} target variables are assigned values in the order
299 specified. In the command @code{COUNT A=A B(1) /B=A B(2).}, the
300 following actions occur:
304 The number of occurrences of 1 between @code{A} and @code{B} is counted.
307 @code{A} is assigned this value.
310 The number of occurrences of 1 between @code{B} and the @strong{new}
311 value of @code{A} is counted.
314 @code{B} is assigned this value.
317 Despite this ordering, all @cmd{COUNT} criterion variables must exist
318 before the procedure is executed---they may not be created as target
319 variables earlier in the command! Break such a command into two
322 The examples below may help to clarify.
326 Assuming @code{Q0}, @code{Q2}, @dots{}, @code{Q9} are numeric variables,
327 the following commands:
331 Count the number of times the value 1 occurs through these variables
332 for each case and assigns the count to variable @code{QCOUNT}.
335 Print out the total number of times the value 1 occurs throughout
336 @emph{all} cases using @cmd{DESCRIPTIVES}. @xref{DESCRIPTIVES}, for
341 COUNT QCOUNT=Q0 TO Q9(1).
342 DESCRIPTIVES QCOUNT /STATISTICS=SUM.
346 Given these same variables, the following commands:
350 Count the number of valid values of these variables for each case and
351 assigns the count to variable @code{QVALID}.
354 Multiplies each value of @code{QVALID} by 10 to obtain a percentage of
355 valid values, using @cmd{COMPUTE}. @xref{COMPUTE}, for details.
358 Print out the percentage of valid values across all cases, using
359 @cmd{DESCRIPTIVES}. @xref{DESCRIPTIVES}, for details.
363 COUNT QVALID=Q0 TO Q9 (LO THRU HI).
364 COMPUTE QVALID=QVALID*10.
365 DESCRIPTIVES QVALID /STATISTICS=MEAN.
369 @node FLIP, IF, COUNT, Data Manipulation
374 FLIP /VARIABLES=var_list /NEWNAMES=var_name.
377 @cmd{FLIP} transposes rows and columns in the active file. It
378 causes cases to be swapped with variables, and vice versa.
380 All variables in the transposed active file are numeric. String
381 variables take on the system-missing value in the transposed file.
383 No subcommands are required. If specified, the VARIABLES subcommand
384 selects variables to be transformed into cases, and variables not
385 specified are discarded. If the VARIABLES subcommand is omitted, all
386 variables are selected for transposition.
388 The variables specified by NEWNAMES, which must be a string variable, is
389 used to give names to the variables created by @cmd{FLIP}. Only the
390 first 8 characters of the variable are used. If
392 specified then the default is a variable named CASE_LBL, if it exists.
393 If it does not then the variables created by FLIP are named VAR000
394 through VAR999, then VAR1000, VAR1001, and so on.
396 When a NEWNAMES variable is available, the names must be canonicalized
397 before becoming variable names. Invalid characters are replaced by
398 letter @samp{V} in the first position, or by @samp{_} in subsequent
399 positions. If the name thus generated is not unique, then numeric
400 extensions are added, starting with 1, until a unique name is found or
401 there are no remaining possibilities. If the latter occurs then the
402 FLIP operation aborts.
404 The resultant dictionary contains a CASE_LBL variable, a string
405 variable of width 8, which stores the names of the variables in the
406 dictionary before the transposition. Variables names longer than 8
407 characters are truncated. If the active file is subsequently
408 transposed using @cmd{FLIP}, this variable can be used to recreate the
409 original variable names.
411 FLIP honors @cmd{N OF CASES} (@pxref{N OF CASES}). It ignores
412 @cmd{TEMPORARY} (@pxref{TEMPORARY}), so that ``temporary''
413 transformations become permanent.
415 @node IF, RECODE, FLIP, Data Manipulation
420 IF condition variable=expression.
422 IF condition vector(index)=expression.
425 The @cmd{IF} transformation conditionally assigns the value of a target
426 expression to a target variable, based on the truth of a test
429 Specify a boolean-valued expression (@pxref{Expressions}) to be tested
430 following the IF keyword. This expression is evaluated for each case.
431 If the value is true, then the value of the expression is computed and
432 assigned to the specified variable. If the value is false or missing,
433 nothing is done. Numeric and short and long string variables may be
434 assigned. When a string expression's width differs from the target
435 variable's width, the string result of the expression is truncated or
436 padded with spaces on the right as necessary. The expression and
437 variable types must match.
439 The target variable may be specified as an element of a vector
440 (@pxref{VECTOR}). In this case, a vector index expression must be
441 specified in parentheses following the vector name. The index
442 expression must evaluate to a numeric value that, after rounding down
443 to the nearest integer, is a valid index for the named vector.
445 Using @cmd{IF} to assign to a variable specified on @cmd{LEAVE}
446 (@pxref{LEAVE}) resets the variable's left state. Therefore,
447 @code{LEAVE} should be specified following @cmd{IF}, not before.
449 When @cmd{IF} is specified following @cmd{TEMPORARY}
450 (@pxref{TEMPORARY}), the @cmd{LAG} function may not be used
453 @node RECODE, SORT CASES, IF, Data Manipulation
458 RECODE var_list (src_value@dots{}=dest_value)@dots{} [INTO var_list].
460 src_value may take the following forms:
467 Open-ended ranges may be specified using LO or LOWEST for num1
468 or HI or HIGHEST for num2.
470 dest_value may take the following forms:
477 @cmd{RECODE} translates data from one range of values to
478 another, via flexible user-specified mappings. Data may be remapped
479 in-place or copied to new variables. Numeric, short string, and long
480 string data can be recoded.
482 Specify the list of source variables, followed by one or more mapping
483 specifications each enclosed in parentheses. If the data is to be
484 copied to new variables, specify INTO, then the list of target
485 variables. String target variables must already have been declared
486 using @cmd{STRING} or another transformation, but numeric target
488 be created on the fly. There must be exactly as many target variables
489 as source variables. Each source variable is remapped into its
490 corresponding target variable.
492 When INTO is not used, the input and output variables must be of the
493 same type. Otherwise, string values can be recoded into numeric values,
494 and vice versa. When this is done and there is no mapping for a
495 particular value, either a value consisting of all spaces or the
496 system-missing value is assigned, depending on variable type.
498 Mappings are considered from left to right. The first src_value that
499 matches the value of the source variable causes the target variable to
500 receive the value indicated by the dest_value. Literal number, string,
501 and range src_value's should be self-explanatory. MISSING as a
502 src_value matches any user- or system-missing value. SYSMIS matches the
503 system missing value only. ELSE is a catch-all that matches anything.
504 It should be the last src_value specified.
506 Numeric and string dest_value's should also be self-explanatory. COPY
507 causes the input values to be copied to the output. This is only value
508 if the source and target variables are of the same type. SYSMIS
509 indicates the system-missing value.
511 If the source variables are strings and the target variables are
512 numeric, then there is one additional mapping available: (CONVERT),
513 which must be the last specified mapping. CONVERT causes a number
514 specified as a string to be converted to a numeric value. If the string
515 cannot be parsed as a number, then the system-missing value is assigned.
517 Multiple recodings can be specified on a single @cmd{RECODE} invocation.
518 Introduce additional recodings with a slash (@samp{/}) to
519 separate them from the previous recodings.
521 @node SORT CASES, , RECODE, Data Manipulation
526 SORT CASES BY var_list.
529 @cmd{SORT CASES} sorts the active file by the values of one or more
532 Specify BY and a list of variables to sort by. By default, variables
533 are sorted in ascending order. To override sort order, specify (D) or
534 (DOWN) after a list of variables to get descending order, or (A) or (UP)
535 for ascending order. These apply to the entire list of variables
538 The sort algorithms used by @cmd{SORT CASES} are stable. That is,
539 records that have equal values of the sort variables will have the
540 same relative order before and after sorting. As a special case,
541 re-sorting an already sorted file will not affect the ordering of
544 @cmd{SORT CASES} is a procedure. It causes the data to be read.
546 @cmd{SORT CASES} attempts to sort the entire active file in main memory.
547 If workspace is exhausted, it falls back to a merge sort algorithm that
548 involves creates numerous temporary files.
550 @cmd{SORT CASES} may not be specified following TEMPORARY.