select

           select datapoints

           cafe

           select, range [,subgroup][,group]

           range    - Defines range of data points to select. This can
                      be either:
                       - Data point range, denoted by the data
                         point number:
                         <n1>[-], while ,  are positive
                         numbers. Data point numbers start from zero.
                         Open intervals can be represented with a
                         "*" instead of the number.
                         If only one number is given, a single
                         data point will be referenced.
                         If <val2> is less than  all but the
                         interval <val2>.. are referenced.
                       - X value range, denoted by float point numbers:
                         <val1>-, while , 
                         represents X values defining the interval to
                         reference. Open intervals can be represented
                         with a *  instead of the value. If <val2> is
                         less than <val1> all but the interval
                         <val2>.. is referenced.
                       - Vector of data point indices. The vector is
                         denoted with [val,val,...,val] (indgen may
                         be used also).
                       - Boolean expressions with X/Y values. All
                         values for which this expression is true are
                         referenced. The expression may contain
                         algebraic formulas combined with comparison
                         operators "lt", "le", "eq", "gt", "ge" as used in IDL
                         comparisons. For each data point a keyword
                         is defined which has meaning and can be used
                         for the boolean expression:
                                 x - The x-column value.
                                 y - The y-column value.
                             error - The error column value.
                          selected - True when the data point is selected.
                               def - True when the data point is defined.
                               x1  - Multi column first column value.
                               x2  - Multi column second column
                                     value.
                               x3  - Multi column third column value.
                         To avoid interference with functions which
                         also can be used a lower/upper case
                         distinction  is made. IDL funktions should
                         be upper case.
                         If no range is given all data points are selected.

                               > select, 2
                                -> select data point 2 (the 3-rd)
                               > select, 5-22
                                -> select data points 5..22 (starting from 0)
                               > select 46-*
                                -> select all data points upwards from point 47.
                               > select, 2.2-5.7
                                 -> select all data points 2.2 <= x <=  5.7
                               > select, *-0.2
                                 -> select all data points up to x<=0.2
                               > select, 0.5-0.2
                                 -> select all data points except those in 0.2..0.5.
                               > select, y lt 0.5
                                -> select all data points with Y-values less than 0.5.
           subgroup - (optional) The data set (subgroup) for which the model
                      should be applied. This can be either the
                      subgroup number or the file name representing
                      the data set. It is possible to set more than
                      one subgroup, either with numbers in brackets
                      ([]) or denoting filenames with wildcards
                      ("*").
                      Default is the first subgroup in current used
                      group.
           group    - (optional) The data group for which the model
                      should be applied.
                      Default is the primary group 0. Must be in
                      range [0..29].

           Changes information about data points used for
           fitting. Data points are not excluded.

               > select, 0.2-7.5,  "test.dat", 3
                 -> select all x values between 0.2 and 7.5 from
                 group 3, subgroup represented by file "test.dat"

           $Id: cafe_select.pro,v 1.11 2004/05/27 09:10:51 goehler Exp $

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