add documentation of rounding processing element (#104)

docs/pe/org.apache.streampipes.processors.transformation.jvm.round.md

@@ -0,0 +1,72 @@
+---
+id: org.apache.streampipes.processors.transformation.jvm.round
+title: Numeric Rounding
+sidebar_label: Numeric Rounding
+---
+
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+
+## Number Rounder
+
+<p align="center">
+    <img src="icon.png" width="150px;" class="pe-image-documentation"/>
+</p>
+
+***
+
+## Description
+
+This processor rounds numeric values to the given decimal places.
+It supports multiple rounding strategies.
+
+***
+
+## Required input
+
+This processor requires an event that provides numerical properties.
+
+***
+
+## Configuration
+
+### Fields to Be Rounded
+
+Select which fields of the event should be rounded.
+
+### Number of Digits
+
+Specify the number of digits after the decimal point to round/keep, e.g., if number is 2.8935 and 'digits' is 3,
+the result will be 2.894.
+
+### Mode of Rounding
+
+Specify the mode of rounding.
+Supported rounding modes:
+* `UP`: Rounding mode to round away from zero. Always increments the digit prior to a non-zero discarded fraction. Note that this rounding mode never decreases the magnitude of the calculated value.
+* `DOWN`: Rounding mode to round towards zero. Never increments the digit prior to a discarded fraction (i.e., truncates). Note that this rounding mode never increases the magnitude of the calculated value.
+* `CEILING`: Rounding mode to round towards positive infinity. If the result is positive, behaves as for `UP`; if negative, behaves as for `DOWN`. Note that this rounding mode never decreases the calculated value
+* `FLOOR`: Rounding mode to round towards negative infinity. If the result is positive, behave as for `DOWN`; if negative, behave as for `UP`. Note that this rounding mode never increases the calculated value.
+* `HALF_UP`: Rounding mode to round towards "nearest neighbor" unless both neighbors are equidistant, in which case round up. Behaves as for `UP` if the discarded fraction is ≥ 0.5; otherwise, behaves as for `DOWN`.
+* `HALF_DOWN`: Rounding mode to round towards "nearest neighbor" unless both neighbors are equidistant, in which case round down. Behaves as for `UP` if the discarded fraction is > 0.5; otherwise, behaves as for `DOWN`.
+* `HALF_EVEN`: Rounding mode to round towards the "nearest neighbor" unless both neighbors are equidistant, in which case, round towards the even neighbor. Behaves as for `HALF_UP` if the digit to the left of the discarded fraction is odd; behaves as for `HALF_DOWN` if it's even. Note that this is the rounding mode that statistically minimizes cumulative error when applied repeatedly over a sequence of calculations.
+
+## Output
+
+The output of this processor is the same event with the fields selected by the ``Fiels to Be Rounded`` parameter rounded
+to ``Number of Digits`` digits.