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                                                  748
       CHAPTER 8                                                             Interactive Features



KEY      TYPE          VALUE

CYX      number        (Optional; meaningful only when Y is present) A factor to convert the largest units
                       along the y axis to the largest units along the x axis. It is required for some calcula-
                       tions (distance, area, and angle) where the units must be equivalent; if not specified,
                       these calculations cannot be performed (which would be the case in situations such
                       as x representing time and y representing temperature). Other calculations (change
                       in x, change in y, and slope) do not require this value.

       The X and Y entries in a measure dictionary are number format arrays that speci-
       fy the units used for measurements in the x and y directions, respectively, and the
       ratio between user space units and the specified units. Y is present only when the
       x and y measurements are in different units or have different ratios; in this case,
       the CYX entry is used to convert y values to x values when appropriate.

                        TABLE 8.112 Entries in a number format dictionary
KEY      TYPE          VALUE

Type     name          (Optional) The type of PDF object that this dictionary describes; must be
                       NumberFormat for a number format dictionary.

U        text string   (Required) A text string specifying a label for displaying the units represented by
                       this dictionary in a user interface; it is recommended that the label use a universally
                       recognized abbreviation.

C        number        (Required) The conversion factor used to multiply a value in partial units of the pre-
                       vious number format array element to obtain a value in the units of this dictionary.
                       When this entry is in the first number format dictionary in the array, its meaning
                       (that is, what it is multiplied by) depends on which entry in the rectilinear measure
                       dictionary (see Table 8.111) references the number format array.

F        name          (Optional; meaningful only for the last dictionary in a number format array) A name
                       indicating whether and in what manner to display a fractional value from the result
                       of converting to the units of this dictionary by means of the C entry. Valid values
                       are:
                          D    Show as decimal to the precision specified by the D entry.
                          F    Show as a fraction with denominator specified by the D entry.
                          R    No fractional part; round to the nearest whole unit.
                          T    No fractional part; truncate to achieve whole units.
                       Default value: D.

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