Basic Examples (3) 

Given a simple tabular with many columns:

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We can simultaneously apply a mathematical function to all its elements:

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Or change the colors of all cells with a given property:

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Scope (6) 

Suppose some data science work produced errors in the final Tabular (as many Round[Missing[]] cells):

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To clean it, we can just apply replacement function to all its columns:

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We can also specify a group of columns (as a Span or List) on which to apply a numeric operation (in the present case, we should exclude the Municipality column because it is made of strings):

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Now on the cleaned table we can also perform an operation with ColumnwiseValue:

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Or with ColumnwiseThread:

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The columns specification can also be given as a list of column names of column indexes:

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Properties and Relations (6) 

TransformTabular[tab,f] is equivalent to TransformColumns with multiple function specifications. Define a Tabular:

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We can apply a transformation for each column with TransformColumns:

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Or apply it a single time with TransformTabular[f,tab]:

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Check that the two results are equal:

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When the function does not involve ColumnwiseValue or ColumnwiseThread, TransformTabular[tab,f] is equivalent to Query (with Normal):

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Check that the two results are equal:

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