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--- transformations:keeptop [2014/10/25 17:19] – created dmitry
+++ transformations:keeptop [2015/05/01 08:58] – dmitry
@@ Line 1: / Line 1: @@
-===== Keep Top Rows =====
+===== Trim Table =====
-This transformation leaves only first N rows and removes all other rows.
+This transformation keeps or removes first or last N rows.
-If you need to remove bottom rows -- add line numbers using [[transformations:enumerate|Enumerate Rows]], sort backwards by row numbers using [[transformations:sort|Sort]] and then apply Keep Top Rows.
+EXAMPLE
+**Source table:** The longest rivers in the world in descending order (by length)
+^  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:** Keep the top three longest rivers
+**Transformation parameters:**
+  * Keep or Remove: Keep
+  * Top or bottom: Top
+  * Number of rows: 3
+**Output table:**
+^  River  ^  Length (km)  ^  Continent  ^
+| Nile  |  6650  |  Africa  |
+| Amazon  |  6400  |  South America  |
+| Yangtze  |  6300  |  Asia  |