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--- transformations:keeptop [2014/10/25 17:19] – created dmitry
+++ transformations:keeptop [2021/05/04 17:46] – craigt
@@ Line 1: / Line 1: @@
-===== Keep Top Rows =====
+{{ transformations:TrimTableAction.png}}
+====== TRIM TABLE ======
+Category: Transform / Filters\\
-This transformation leaves only first N rows and removes all other rows.
+\\
+=====Description=====
+This action keeps or removes the 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.
+\\
+=====Use cases=====
+Reduce the size of a larger dataset to a specific number of rows during the initial build of a workflow.  Remove the //Trim table// action when the workflow is complete, to process the entire dataset.
+Remove extraneous metadata from the top or bottom of a dataset.\\
+\\
+=====Action settings=====
+^Setting ^Description ^
+|Keep only/Remove|Select whether N number of rows will be kept or removed.|
+|Top/Bottom|Select whether the rows at the top or bottom of the table will be kept/removed.|
+|N rows<sup>*</sup>|Enter/Select the number of rows to keep/remove.|
+<sup>*</sup> Setting can be specified using a [[:parameters|parameter]].
+\\
+=====Examples=====
+**Objective:** Keep the top three longest rivers.\\
+\\
+**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  |
+\\
+**Action parameters:**
+> Keep or Remove is "Keep"
+> Top or Bottom is "Top"
+> Number of rows is "3"
+\\
+**Result:**
+^River  ^Length (km)  ^Continent  ^
+| Nile  |  6650|Africa  |
+| Amazon  |  6400|South America  |
+| Yangtze  |  6300|Asia  |
+\\
+=====See also=====
+  * [[transformations:keepremovematching|Keep/remove matching]]