transpose

Numpy transpose of 1D array not giving expected result

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NumPy’s transpose() effectively reverses the shape of an array. If the array is one-dimensional, this means it has no effect. In NumPy, the arrays array([1, 2, 3]) and array([1, 2, 3]) are actually the same – they only differ in whitespace. What you probably want are the corresponding two-dimensional arrays, for which transpose() would work … Read more

Transpose column to row with Spark

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Spark >= 3.4 You can use built-in melt method. With Python: df.melt( ids=[“A”], values=[“col_1”, “col_2″], variableColumnName=”key”, valueColumnName=”val” ) with Scala df.melt(Array($”A”), Array($”col_1″, $”col_2″), “key”, “val”) Spark < 3.4 It is relatively simple to do with basic Spark SQL functions. Python from pyspark.sql.functions import array, col, explode, struct, lit df = sc.parallelize([(1, 0.0, 0.6), (1, 0.6, … Read more

Transpose latest rows per user to columns

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Use crosstab() from the tablefunc module. SELECT * FROM crosstab( $$SELECT user_id, user_name, rn, email_address FROM ( SELECT u.user_id, u.user_name, e.email_address , row_number() OVER (PARTITION BY u.user_id ORDER BY e.creation_date DESC NULLS LAST) AS rn FROM usr u LEFT JOIN email_tbl e USING (user_id) ) sub WHERE rn < 4 ORDER BY user_id $$ , … Read more

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