@chapter Data transformations
@cindex transformations
-The PSPP procedures examined in this chapter manipulate data and
+The @pspp{} procedures examined in this chapter manipulate data and
prepare the active dataset for later analyses. They do not produce output,
as a rule.
@display
AGGREGATE
- OUTFILE=@{*,'file-name',file_handle@} [MODE=@{REPLACE, ADDVARIABLES@}]
+ OUTFILE=@{*,'@var{file_name}',@var{file_handle}@} [MODE=@{REPLACE, ADDVARIABLES@}]
/PRESORTED
/DOCUMENT
/MISSING=COLUMNWISE
- /BREAK=var_list
- /dest_var['label']@dots{}=agr_func(src_vars, args@dots{})@dots{}
+ /BREAK=@var{var_list}
+ /@var{dest_var}['@var{label}']@dots{}=@var{agr_func}(@var{src_vars}, @var{args}@dots{})@dots{}
@end display
@cmd{AGGREGATE} summarizes groups of cases into single cases.
variables called @dfn{break variables}. Several functions are available
for summarizing case contents.
-The OUTFILE subcommand is required and must appear first. Specify a
+The @subcmd{OUTFILE} subcommand is required and must appear first. Specify a
system file or portable file by file name or file
handle (@pxref{File Handles}), or a dataset by its name
(@pxref{Datasets}).
The aggregated cases are written to this file. If @samp{*} is
specified, then the aggregated cases replace the active dataset's data.
-Use of OUTFILE to write a portable file is a PSPP extension.
+Use of @subcmd{OUTFILE} to write a portable file is a @pspp{} extension.
-If OUTFILE=@samp{*} is given, then the subcommand MODE may also be
+If @subcmd{OUTFILE=*} is given, then the subcommand @subcmd{MODE} may also be
specified.
-The mode subcommand has two possible values: ADDVARIABLES or REPLACE.
-In REPLACE mode, the entire active dataset is replaced by a new dataset
+The mode subcommand has two possible values: @subcmd{ADDVARIABLES} or @subcmd{REPLACE}.
+In @subcmd{REPLACE} mode, the entire active dataset is replaced by a new dataset
which contains just the break variables and the destination varibles.
In this mode, the new file will contain as many cases as there are
unique combinations of the break variables.
-In ADDVARIABLES mode, the destination variables will be appended to
+In @subcmd{ADDVARIABLES} mode, the destination variables will be appended to
the existing active dataset.
Cases which have identical combinations of values in their break
variables, will receive identical values for the destination variables.
The number of cases in the active dataset will remain unchanged.
-Note that if ADDVARIABLES is specified, then the data @emph{must} be
+Note that if @subcmd{ADDVARIABLES} is specified, then the data @emph{must} be
sorted on the break variables.
By default, the active dataset will be sorted based on the break variables
before aggregation takes place. If the active dataset is already sorted
or otherwise grouped in terms of the break variables, specify
-PRESORTED to save time.
-PRESORTED is assumed if MODE=ADDVARIABLES is used.
+@subcmd{PRESORTED} to save time.
+@subcmd{PRESORTED} is assumed if @subcmd{MODE=ADDVARIABLES} is used.
-Specify DOCUMENT to copy the documents from the active dataset into the
+Specify @subcmd{DOCUMENT} to copy the documents from the active dataset into the
aggregate file (@pxref{DOCUMENT}). Otherwise, the aggregate file will
not contain any documents, even if the aggregate file replaces the
active dataset.
-Normally, only a single case (for SD and SD., two cases) need be
+Normally, only a single case (for @subcmd{SD} and @subcmd{SD}., two cases) need be
non-missing in each group for the aggregate variable to be
-non-missing. Specifying /MISSING=COLUMNWISE inverts this behavior, so
+non-missing. Specifying @subcmd{/MISSING=COLUMNWISE} inverts this behavior, so
that the aggregate variable becomes missing if any aggregated value is
missing.
-If PRESORTED, DOCUMENT, or MISSING are specified, they must appear
-between OUTFILE and BREAK.
+If @subcmd{PRESORTED}, @subcmd{DOCUMENT}, or @subcmd{MISSING} are specified, they must appear
+between @subcmd{OUTFILE} and @subcmd{BREAK}.
-At least one break variable must be specified on BREAK, a
+At least one break variable must be specified on @subcmd{BREAK}, a
required subcommand. The values of these variables are used to divide
the active dataset into groups to be summarized. In addition, at least
one @var{dest_var} must be specified.
Each set must have exactly as many source variables as aggregation
variables. Each aggregation variable receives the results of applying
the specified aggregation function to the corresponding source
-variable. The MEAN, MEDIAN, SD, and SUM aggregation functions may only be
+variable. The @subcmd{MEAN}, @subcmd{MEDIAN}, @subcmd{SD}, and @subcmd{SUM}
+aggregation functions may only be
applied to numeric variables. All the rest may be applied to numeric
and string variables.
The available aggregation functions are as follows:
@table @asis
-@item FGT(var_name, value)
+@item @subcmd{FGT(@var{var_name}, @var{value})}
Fraction of values greater than the specified constant. The default
format is F5.3.
-@item FIN(var_name, low, high)
+@item @subcmd{FIN(@var{var_name}, @var{low}, @var{high})}
Fraction of values within the specified inclusive range of constants.
The default format is F5.3.
-@item FLT(var_name, value)
+@item @subcmd{FLT(@var{var_name}, @var{value})}
Fraction of values less than the specified constant. The default
format is F5.3.
-@item FIRST(var_name)
+@item @subcmd{FIRST(@var{var_name})}
First non-missing value in break group. The aggregation variable
receives the complete dictionary information from the source variable.
-The sort performed by AGGREGATE (and by SORT CASES) is stable, so that
+The sort performed by @cmd{AGGREGATE} (and by @cmd{SORT CASES}) is stable, so that
the first case with particular values for the break variables before
sorting will also be the first case in that break group after sorting.
-@item FOUT(var_name, low, high)
+@item @subcmd{FOUT(@var{var_name}, @var{low}, @var{high})}
Fraction of values strictly outside the specified range of constants.
The default format is F5.3.
-@item LAST(var_name)
+@item @subcmd{LAST(@var{var_name})}
Last non-missing value in break group. The aggregation variable
receives the complete dictionary information from the source variable.
-The sort performed by AGGREGATE (and by SORT CASES) is stable, so that
+The sort performed by @cmd{AGGREGATE} (and by @cmd{SORT CASES}) is stable, so that
the last case with particular values for the break variables before
sorting will also be the last case in that break group after sorting.
-@item MAX(var_name)
+@item @subcmd{MAX(@var{var_name})}
Maximum value. The aggregation variable receives the complete
dictionary information from the source variable.
-@item MEAN(var_name)
+@item @subcmd{MEAN(@var{var_name})}
Arithmetic mean. Limited to numeric values. The default format is
F8.2.
-@item MEDIAN(var_name)
+@item @subcmd{MEDIAN(@var{var_name})}
The median value. Limited to numeric values. The default format is F8.2.
-@item MIN(var_name)
+@item @subcmd{MIN(@var{var_name})}
Minimum value. The aggregation variable receives the complete
dictionary information from the source variable.
-@item N(var_name)
+@item @subcmd{N(@var{var_name})}
Number of non-missing values. The default format is F7.0 if weighting
is not enabled, F8.2 if it is (@pxref{WEIGHT}).
-@item N
+@item @subcmd{N}
Number of cases aggregated to form this group. The default format is
F7.0 if weighting is not enabled, F8.2 if it is (@pxref{WEIGHT}).
-@item NMISS(var_name)
+@item @subcmd{NMISS(@var{var_name})}
Number of missing values. The default format is F7.0 if weighting is
not enabled, F8.2 if it is (@pxref{WEIGHT}).
-@item NU(var_name)
+@item @subcmd{NU(@var{var_name})}
Number of non-missing values. Each case is considered to have a weight
of 1, regardless of the current weighting variable (@pxref{WEIGHT}).
The default format is F7.0.
-@item NU
+@item @subcmd{NU}
Number of cases aggregated to form this group. Each case is considered
to have a weight of 1, regardless of the current weighting variable.
The default format is F7.0.
-@item NUMISS(var_name)
+@item @subcmd{NUMISS(@var{var_name})}
Number of missing values. Each case is considered to have a weight of
1, regardless of the current weighting variable. The default format is F7.0.
-@item PGT(var_name, value)
+@item @subcmd{PGT(@var{var_name}, @var{value})}
Percentage between 0 and 100 of values greater than the specified
constant. The default format is F5.1.
-@item PIN(var_name, low, high)
+@item @subcmd{PIN(@var{var_name}, @var{low}, @var{high})}
Percentage of values within the specified inclusive range of
constants. The default format is F5.1.
-@item PLT(var_name, value)
+@item @subcmd{PLT(@var{var_name}, @var{value})}
Percentage of values less than the specified constant. The default
format is F5.1.
-@item POUT(var_name, low, high)
+@item @subcmd{POUT(@var{var_name}, @var{low}, @var{high})}
Percentage of values strictly outside the specified range of
constants. The default format is F5.1.
-@item SD(var_name)
+@item @subcmd{SD(@var{var_name})}
Standard deviation of the mean. Limited to numeric values. The
default format is F8.2.
-@item SUM(var_name)
+@item @subcmd{SUM(@var{var_name})}
Sum. Limited to numeric values. The default format is F8.2.
@end table
Aggregation functions compare string values in terms of internal
-character codes. On most modern computers, this is a form of ASCII.
+character codes.
+On most modern computers, this is @acronym{ASCII} or a superset thereof.
The aggregation functions listed above exclude all user-missing values
from calculations. To include user-missing values, insert a period
@vindex AUTORECODE
@display
-AUTORECODE VARIABLES=src_vars INTO dest_vars
+AUTORECODE VARIABLES=@var{src_vars} INTO @var{dest_vars}
[ /DESCENDING ]
[ /PRINT ]
[ /GROUP ]
+ [ /BLANK = @{VALID, MISSING@} ]
@end display
The @cmd{AUTORECODE} procedure considers the @var{n} values that a variable
takes on and maps them onto values 1@dots{}@var{n} on a new numeric
variable.
-Subcommand VARIABLES is the only required subcommand and must come
-first. Specify VARIABLES, an equals sign (@samp{=}), a list of source
-variables, INTO, and a list of target variables. There must the same
+Subcommand @subcmd{VARIABLES} is the only required subcommand and must come
+first. Specify @subcmd{VARIABLES}, an equals sign (@samp{=}), a list of source
+variables, @subcmd{INTO}, and a list of target variables. There must the same
number of source and target variables. The target variables must not
already exist.
is based on character code comparisons) are recoded to increasing values
of its target variable. To cause increasing values of a source variable
to be recoded to decreasing values of its target variable (@var{n} down
-to 1), specify DESCENDING.
+to 1), specify @subcmd{DESCENDING}.
-PRINT is currently ignored.
+@subcmd{PRINT} is currently ignored.
-The GROUP subcommand is relevant only if more than one variable is to be
+The @subcmd{GROUP} subcommand is relevant only if more than one variable is to be
recoded. It causes a single mapping between source and target values to
be used, instead of one map per variable.
+If @subcmd{/BLANK=MISSING} is given, then string variables which contain only
+whitespace are recoded as SYSMIS. If @subcmd{/BLANK=VALID} is given then they
+will be allocated a value like any other. @subcmd{/BLANK} is not relevant
+to numeric values. @subcmd{/BLANK=VALID} is the default.
+
@cmd{AUTORECODE} is a procedure. It causes the data to be read.
@node COMPUTE
@vindex COMPUTE
@display
-COMPUTE variable = expression.
+COMPUTE @var{variable} = @var{expression}.
+@end display
or
-COMPUTE vector(index) = expression.
+@display
+COMPUTE vector(@var{index}) = @var{expression}.
@end display
@cmd{COMPUTE} assigns the value of an expression to a target
they can be used as targets for @cmd{COMPUTE}.
The target variable may be specified as an element of a vector
-(@pxref{VECTOR}). In this case, a vector index expression must be
-specified in parentheses following the vector name. The index
-expression must evaluate to a numeric value that, after rounding down
+(@pxref{VECTOR}). In this case, an expression @var{index} must be
+specified in parentheses following the vector name. The expression @var{index}
+must evaluate to a numeric value that, after rounding down
to the nearest integer, is a valid index for the named vector.
Using @cmd{COMPUTE} to assign to a variable specified on @cmd{LEAVE}
@vindex COUNT
@display
-COUNT var_name = var@dots{} (value@dots{}).
+COUNT @var{var_name} = @var{var}@dots{} (@var{value}@dots{}).
-Each value takes one of the following forms:
- number
- string
- num1 THRU num2
+Each @var{value} takes one of the following forms:
+ @var{number}
+ @var{string}
+ @var{num1} THRU @var{num2}
MISSING
SYSMIS
-In addition, num1 and num2 can be LO or LOWEST, or HI or HIGHEST,
-respectively.
+where @var{num1} is a numeric expression or the words @subcmd{LO} or @subcmd{LOWEST}
+ and @var{num2} is a numeric expression or @subcmd{HI} or @subcmd{HIGHEST}.
@end display
@cmd{COUNT} creates or replaces a numeric @dfn{target} variable that
values. They are @strong{not} treated as system-missing values.
User-missing values that are criterion values or inside ranges of
criterion values are counted as any other values. However (for numeric
-variables), keyword MISSING may be used to refer to all system-
+variables), keyword @subcmd{MISSING} may be used to refer to all system-
and user-missing values.
@cmd{COUNT} target variables are assigned values in the order
-specified. In the command @code{COUNT A=A B(1) /B=A B(2).}, the
+specified. In the command @subcmd{COUNT @var{A}=@var{A} @var{B}(1) /@var{B}=@var{A} @var{B}(2).}, the
following actions occur:
@itemize @minus
@item
-The number of occurrences of 1 between @code{A} and @code{B} is counted.
+The number of occurrences of 1 between @var{A} and @var{B} is counted.
@item
-@code{A} is assigned this value.
+@var{A} is assigned this value.
@item
-The number of occurrences of 1 between @code{B} and the @strong{new}
-value of @code{A} is counted.
+The number of occurrences of 1 between @var{B} and the @strong{new}
+value of @var{A} is counted.
@item
-@code{B} is assigned this value.
+@var{B} is assigned this value.
@end itemize
Despite this ordering, all @cmd{COUNT} criterion variables must exist
@vindex FLIP
@display
-FLIP /VARIABLES=var_list /NEWNAMES=var_name.
+FLIP /VARIABLES=@var{var_list} /NEWNAMES=@var{var_name}.
@end display
@cmd{FLIP} transposes rows and columns in the active dataset. It
All variables in the transposed active dataset are numeric. String
variables take on the system-missing value in the transposed file.
-No subcommands are required. If specified, the VARIABLES subcommand
+@subcmd{N} subcommands are required. If specified, the @subcmd{VARIABLES} subcommand
selects variables to be transformed into cases, and variables not
-specified are discarded. If the VARIABLES subcommand is omitted, all
+specified are discarded. If the @subcmd{VARIABLES} subcommand is omitted, all
variables are selected for transposition.
-The variables specified by NEWNAMES, which must be a string variable, is
+The variables specified by @subcmd{NEWNAMES}, which must be a
+string variable, is
used to give names to the variables created by @cmd{FLIP}. Only the
first 8 characters of the variable are used. If
-NEWNAMES is not
+@subcmd{NEWNAMES} is not
specified then the default is a variable named CASE_LBL, if it exists.
-If it does not then the variables created by FLIP are named VAR000
+If it does not then the variables created by @cmd{FLIP} are named VAR000
through VAR999, then VAR1000, VAR1001, and so on.
-When a NEWNAMES variable is available, the names must be canonicalized
+When a @subcmd{NEWNAMES} variable is available, the names must be canonicalized
before becoming variable names. Invalid characters are replaced by
letter @samp{V} in the first position, or by @samp{_} in subsequent
positions. If the name thus generated is not unique, then numeric
extensions are added, starting with 1, until a unique name is found or
there are no remaining possibilities. If the latter occurs then the
-FLIP operation aborts.
+@cmd{FLIP} operation aborts.
The resultant dictionary contains a CASE_LBL variable, a string
variable of width 8, which stores the names of the variables in the
transposed using @cmd{FLIP}, this variable can be used to recreate the
original variable names.
-FLIP honors @cmd{N OF CASES} (@pxref{N OF CASES}). It ignores
+@cmd{FLIP} honors @cmd{N OF CASES} (@pxref{N OF CASES}). It ignores
@cmd{TEMPORARY} (@pxref{TEMPORARY}), so that ``temporary''
transformations become permanent.
@vindex IF
@display
-IF condition variable=expression.
+IF @var{condition} @var{variable}=@var{expression}.
+@end display
or
-IF condition vector(index)=expression.
+@display
+IF @var{condition} vector(@var{index})=@var{expression}.
@end display
The @cmd{IF} transformation conditionally assigns the value of a target
expression.
Specify a boolean-valued expression (@pxref{Expressions}) to be tested
-following the IF keyword. This expression is evaluated for each case.
+following the @cmd{IF} keyword. This expression is evaluated for each case.
If the value is true, then the value of the expression is computed and
assigned to the specified variable. If the value is false or missing,
nothing is done. Numeric and string variables may be
@section RECODE
@vindex RECODE
+The @cmd{RECODE} command is used to transform existing values into other,
+user specified values.
+The general form is:
+
@display
-RECODE var_list (src_value@dots{}=dest_value)@dots{} [INTO var_list].
+RECODE @var{src_vars}
+ (@var{src_value} @var{src_value} @dots{} = @var{dest_value})
+ (@var{src_value} @var{src_value} @dots{} = @var{dest_value})
+ (@var{src_value} @var{src_value} @dots{} = @var{dest_value}) @dots{}
+ [INTO @var{dest_vars}].
+@end display
-src_value may take the following forms:
- number
- string
- num1 THRU num2
- MISSING
- SYSMIS
- ELSE
-Open-ended ranges may be specified using LO or LOWEST for num1
-or HI or HIGHEST for num2.
+Following the @cmd{RECODE} keyword itself comes @var{src_vars} which is a list
+of variables whose values are to be transformed.
+These variables may be string variables or they may be numeric.
+However the list must be homogeneous; you may not mix string variables and
+numeric variables in the same recoding.
+
+After the list of source variables, there should be one or more @dfn{mappings}.
+Each mapping is enclosed in parentheses, and contains the source values and
+a destination value separated by a single @samp{=}.
+The source values are used to specify the values in the dataset which
+need to change, and the destination value specifies the new value
+to which they should be changed.
+Each @var{src_value} may take one of the following forms:
+@itemize @bullet
+@item @var{number}
+If the source variables are numeric then @var{src_value} may be a literal
+number.
+@item @var{string}
+If the source variables are string variables then @var{src_value} may be a
+literal string (like all strings, enclosed in single or double quotes).
+@item @var{num1} THRU @var{num2}
+This form is valid only when the source variables are numeric.
+It specifies all values in the range [@var{num1}, @var{num2}].
+Normally you would ensure that @var{num2} is greater than or equal to
+@var{num1}.
+If @var{num1} however is greater than @var{num2}, then the range
+[@var{num2},@var{num1}] will be used instead.
+Open-ended ranges may be specified using @samp{LO} or @samp{LOWEST}
+for @var{num1}
+or @samp{HI} or @samp{HIGHEST} for @var{num2}.
+@item @samp{MISSING}
+The literal keyword @samp{MISSING} matches both system missing and user
+missing values.
+It is valid for both numeric and string variables.
+@item @samp{SYSMIS}
+The literal keyword @samp{SYSMIS} matches system missing
+values.
+It is valid for both numeric variables only.
+@item @samp{ELSE}
+The @samp{ELSE} keyword may be used to match any values which are
+not matched by any other @var{src_value} appearing in the command.
+If this keyword appears, it should be used in the last mapping of the
+command.
+@end itemize
-dest_value may take the following forms:
- num
- string
- SYSMIS
- COPY
-@end display
+After the source variables comes an @samp{=} and then the @var{dest_value}.
+The @var{dest_value} may take any of the following forms:
+@itemize @bullet
+@item @var{number}
+A literal numeric value to which the source values should be changed.
+This implies the destination variable must be numeric.
+@item @var{string}
+A literal string value (enclosed in quotation marks) to which the source
+values should be changed.
+This implies the destination variable must be a string variable.
+@item @samp{SYSMIS}
+The keyword @samp{SYSMIS} changes the value to the system missing value.
+This implies the destination variable must be numeric.
+@item @samp{COPY}
+The special keyword @samp{COPY} means that the source value should not be
+modified, but
+copied directly to the destination value.
+This is meaningful only if @samp{INTO @var{dest_vars}} is specified.
+@end itemize
-@cmd{RECODE} translates data from one range of values to
-another, via flexible user-specified mappings. Data may be remapped
-in-place or copied to new variables. Numeric and
-string data can be recoded.
-
-Specify the list of source variables, followed by one or more mapping
-specifications each enclosed in parentheses. If the data is to be
-copied to new variables, specify INTO, then the list of target
-variables. String target variables must already have been declared
-using @cmd{STRING} or another transformation, but numeric target
-variables can
-be created on the fly. There must be exactly as many target variables
-as source variables. Each source variable is remapped into its
-corresponding target variable.
-
-When INTO is not used, the input and output variables must be of the
-same type. Otherwise, string values can be recoded into numeric values,
-and vice versa. When this is done and there is no mapping for a
-particular value, either a value consisting of all spaces or the
-system-missing value is assigned, depending on variable type.
-
-Mappings are considered from left to right. The first src_value that
-matches the value of the source variable causes the target variable to
-receive the value indicated by the dest_value. Literal number, string,
-and range src_value's should be self-explanatory. MISSING as a
-src_value matches any user- or system-missing value. SYSMIS matches the
-system missing value only. ELSE is a catch-all that matches anything.
-It should be the last src_value specified.
-
-Numeric and string dest_value's should be self-explanatory. COPY
-causes the input values to be copied to the output. This is only valid
-if the source and target variables are of the same type. SYSMIS
-indicates the system-missing value.
-
-If the source variables are strings and the target variables are
-numeric, then there is one additional mapping available: (CONVERT),
-which must be the last specified mapping. CONVERT causes a number
-specified as a string to be converted to a numeric value. If the string
-cannot be parsed as a number, then the system-missing value is assigned.
-
-Multiple recodings can be specified on a single @cmd{RECODE} invocation.
+Mappings are considered from left to right.
+Therefore, if a value is matched by a @var{src_value} from more than
+one mapping, the first (leftmost) mapping which matches will be considered.
+Any subsequent matches will be ignored.
+
+The clause @samp{INTO @var{dest_vars}} is optional.
+The behaviour of the command is slightly different depending on whether it
+appears or not.
+
+If @samp{INTO @var{dest_vars}} does not appear, then values will be recoded
+``in place´´. This means that the recoded values are written back to the
+source variables from whence the original values came.
+In this case, the @var{dest_value} for every mapping must imply a value which
+has the same type as the @var{src_value}.
+For example, if the source value is a string value, it is not permissible for
+@var{dest_value} to be @samp{SYSMIS} or another forms which implies a numeric
+result.
+The following example two numeric variables @var{x} and @var{y} are recoded
+in place.
+Zero is recoded to 99, the values 1 to 10 inclusive are unchanged,
+values 1000 and higher are recoded to the system-missing value and all other
+values are changed to 999:
+@example
+recode @var{x} @var{y}
+ (0 = 99)
+ (1 THRU 10 = COPY)
+ (1000 THRU HIGHEST = SYSMIS)
+ (ELSE = 999).
+@end example
+
+If @samp{INTO @var{dest_vars}} is given, then recoded values are written
+into the variables specified in @var{dest_vars}, which must therefore
+ contain a list of valid variable names.
+The number of variables in @var{dest_vars} must be the same as the number
+of variables in @var{src_vars}
+and the respective order of the variables in @var{dest_vars} corresponds to
+the order of @var{src_vars}.
+That is to say, recoded values whose
+original value came from the @var{n}th variable in @var{src_vars} will be
+placed into the @var{n}th variable in @var{dest_vars}.
+The source variables will be unchanged.
+If any mapping implies a string as its destination value, then the respective
+destination variable must already exist, or
+have been declared using @cmd{STRING} or another transformation.
+Numeric variables however will be automatically created if they don't already
+exist.
+The following example deals with two source variables, @var{a} and @var{b}
+which contain string values. Hence there are two destination variables
+@var{v1} and @var{v2}.
+Any cases where @var{a} or @var{b} contain the values @samp{apple},
+@samp{pear} or @samp{pomegranate} will result in @var{v1} or @var{v2} being
+filled with the string @samp{fruit} whilst cases with
+@samp{tomato}, @samp{lettuce} or @samp{carrot} will result in @samp{vegetable}.
+Any other values will produce the result @samp{unknown}:
+@example
+string @var{v1} (a20).
+string @var{v2} (a20).
+
+recode @var{a} @var{b}
+ ("apple" "pear" "pomegranate" = "fruit")
+ ("tomato" "lettuce" "carrot" = "vegetable")
+ (ELSE = "unknown")
+ into @var{v1} @var{v2}.
+@end example
+
+There is one very special mapping, not mentioned above.
+If the source variable is a string variable
+then a mapping may be specified as @samp{(CONVERT)}.
+This mapping, if it appears must be the last mapping given and
+the @samp{INTO @var{dest_vars}} clause must also be given and
+must not refer to a string variable.
+@samp{CONVERT} causes a number specified as a string to
+be converted to a numeric value.
+For example it will convert the string @samp{"3"} into the numeric
+value 3 (note that it will not convert @samp{three} into 3).
+If the string cannot be parsed as a number, then the system-missing value
+is assigned instead.
+In the following example, cases where the value of @var{x} (a string variable)
+is the empty string, are recoded to 999 and all others are converted to the
+numeric equivalent of the input value. The results are placed into the
+numeric variable @var{y}:
+@example
+recode @var{x}
+ ("" = 999)
+ (convert)
+ into @var{y}.
+@end example
+
+It is possible to specify multiple recodings on a single command.
Introduce additional recodings with a slash (@samp{/}) to
-separate them from the previous recodings.
+separate them from the previous recodings:
+@example
+recode
+ @var{a} (2 = 22) (else = 99)
+ /@var{b} (1 = 3) into @var{z}
+ .
+@end example
+@noindent Here we have two recodings. The first affects the source variable
+@var{a} and recodes in-place the value 2 into 22 and all other values to 99.
+The second recoding copies the values of @var{b} into the the variable @var{z},
+changing any instances of 1 into 3.
@node SORT CASES
@section SORT CASES
@vindex SORT CASES
@display
-SORT CASES BY var_list[(@{D|A@}] [ var_list[(@{D|A@}] ] ...
+SORT CASES BY @var{var_list}[(@{D|A@}] [ @var{var_list}[(@{D|A@}] ] ...
@end display
@cmd{SORT CASES} sorts the active dataset by the values of one or more
variables.
-Specify BY and a list of variables to sort by. By default, variables
-are sorted in ascending order. To override sort order, specify (D) or
-(DOWN) after a list of variables to get descending order, or (A) or (UP)
+Specify @subcmd{BY} and a list of variables to sort by. By default, variables
+are sorted in ascending order. To override sort order, specify @subcmd{(D)} or
+@subcmd{(DOWN)} after a list of variables to get descending order, or @subcmd{(A)} or @subcmd{(UP)}
for ascending order. These apply to all the listed variables
-up until the preceding (A), (D), (UP) or (DOWN).
+up until the preceding @subcmd{(A)}, @subcmd{(D)}, @subcmd{(UP)} or @subcmd{(DOWN)}.
The sort algorithms used by @cmd{SORT CASES} are stable. That is,
records that have equal values of the sort variables will have the
If workspace is exhausted, it falls back to a merge sort algorithm that
involves creates numerous temporary files.
-@cmd{SORT CASES} may not be specified following TEMPORARY.
+@cmd{SORT CASES} may not be specified following @cmd{TEMPORARY}.
projects / pspp / blobdiff