Differences

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--- transformations:filter [2015/03/20 21:33] – elenap
+++ transformations:filter [2015/04/10 11:29] – elenap
@@ Line 1: / Line 1: @@
 ===== Filter by Condition =====
-This transformation calculates an [[syntax:start|expression]] for every row (without adding a new column) and leaves only rows where this expression is true. Other rows are removed.
+This transformation calculates an [[syntax:start|expression]] for every row (without adding a new column) and keeps only rows where this expression is true. Other rows are removed.
 The expression should be logical and return a boolean value (i.e. either true or false).
@@ Line 16: / Line 16: @@
 If no rows satisfy the condition then all rows get removed.
+**Example of transformation**
+**Source table:** The longest rivers in the world
+^  River  ^  Length (km)  ^  Continent  ^
+| Nile  |  6650  |  Africa  |
+| Amazon  |  6400  |  South America  |
+| Yangtze  |  6300  |  Asia  |
+| Mississippi  |  6275  |  North America  |
+| Yenisei  |  5539  |  Asia  |
+| Yellow River  |  5464  |  Asia  |
+| Ob  |  5410  |  Asia  |
+| Paraná  |  4880  |  South America  |
+**Objective:** Find all rivers that are longer than 6000 km
+**Transformation parameters:**
+  * Column: Length (km)
+  * Expression: [Length (km)] > 6000
+**Output table:**
+^  River  ^  Length (km)  ^  Continent  ^
+| Nile  |  6650  |  Africa  |
+| Amazon  |  6400  |  South America  |
+| Yangtze  |  6300  |  Asia  |
+| Mississippi  |  6275  |  North America  |
+=== See also ===
+  * [[transformations:selectionfilter|Filter]]