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https://issues.apache.org/jira/browse/FREEMARKER-144?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17120631#comment-17120631
]
Siegfried Goeschl commented on FREEMARKER-144:
----------------------------------------------
Got a POC working
{noformat}
<#ftl output_format="plainText">
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<#assign cvsFormat = CSVTool.formats["DEFAULT"].withHeader().withDelimiter(';')>
<#assign csvParser = CSVTool.parse(DataSources.get(0), cvsFormat)>
<#assign users = DataFrameTool.toDataFrame(csvParser)>
Original Data
=============================================================================
${DataFrameTool.print(users)}
Select & Sort Users
=============================================================================
users.
.select("(name == 'Schmitt' || name == 'Meier') && country == 'Germany'")
.sort("name", DataFrameTool.sortOrder["ASCENDING"])
${DataFrameTool.print(users
.select("(name == 'Schmitt' || name == 'Meier') && country == 'Germany'")
.sort("name", DataFrameTool.sortOrder["ASCENDING"]))}
Head of Users
=============================================================================
users.head(2)
${DataFrameTool.print(users.head(2))}
Remove Column From Users
=============================================================================
users.removeColumn("age"))
${DataFrameTool.print(users.removeColumn("age"))}
{noformat}
{noformat}
Original Data
=============================================================================
┌────────────┬────────────┬────────────┐
│#name │#age │#country │
├────────────┼────────────┼────────────┤
│Schmitt │24 │Germany │
├────────────┼────────────┼────────────┤
│Parker │45 │USA │
├────────────┼────────────┼────────────┤
│Meier │20 │Germany │
├────────────┼────────────┼────────────┤
│Schmitt │30 │France │
├────────────┼────────────┼────────────┤
│Peter │44 │Germany │
├────────────┼────────────┼────────────┤
│Meier │24 │Germany │
├────────────┼────────────┼────────────┤
│Green │33 │UK │
├────────────┼────────────┼────────────┤
│Schmitt │30 │Germany │
├────────────┼────────────┼────────────┤
│Meier │30 │Germany │
└────────────┴────────────┴────────────┘
Select & Sort Users
=============================================================================
users.
.select("(name == 'Schmitt' || name == 'Meier') && country == 'Germany'")
.sort("name", DataFrameTool.sortOrder["ASCENDING"])
┌────────────┬────────────┬────────────┐
│#name │#age │#country │
├────────────┼────────────┼────────────┤
│Meier │20 │Germany │
├────────────┼────────────┼────────────┤
│Meier │24 │Germany │
├────────────┼────────────┼────────────┤
│Meier │30 │Germany │
├────────────┼────────────┼────────────┤
│Schmitt │24 │Germany │
├────────────┼────────────┼────────────┤
│Schmitt │30 │Germany │
└────────────┴────────────┴────────────┘
Head of Users
=============================================================================
users.head(2)
┌────────────┬────────────┬────────────┐
│#name │#age │#country │
├────────────┼────────────┼────────────┤
│Schmitt │24 │Germany │
├────────────┼────────────┼────────────┤
│Parker │45 │USA │
└────────────┴────────────┴────────────┘
Remove Column From Users
=============================================================================
users.removeColumn("age"))
┌────────────┬────────────┐
│#name │#country │
├────────────┼────────────┤
│Schmitt │Germany │
├────────────┼────────────┤
│Parker │USA │
├────────────┼────────────┤
│Meier │Germany │
├────────────┼────────────┤
│Schmitt │France │
├────────────┼────────────┤
│Peter │Germany │
├────────────┼────────────┤
│Meier │Germany │
├────────────┼────────────┤
│Green │UK │
├────────────┼────────────┤
│Schmitt │Germany │
├────────────┼────────────┤
│Meier │Germany │
└────────────┴────────────┘
{noformat}
> [freemarker-cli] Proof Of Concept for providing DataFrames
> ----------------------------------------------------------
>
> Key: FREEMARKER-144
> URL: https://issues.apache.org/jira/browse/FREEMARKER-144
> Project: Apache Freemarker
> Issue Type: Task
> Reporter: Siegfried Goeschl
> Assignee: Siegfried Goeschl
> Priority: Major
>
> Sometime users need to massage tabular data coming from CSV or an Excel
> sheet, eg.. joining on columns
> * There is some ad-hoc code in the FreeMarker Generator CSV tool
> * I had a look at available DataFrame libraries (see
> https://medium.com/@thijser/doing-cool-data-science-in-java-how-3-dataframe-libraries-stack-up-5e6ccb7b437)
> I finally found [nRo/DataFrame|https://github.com/nRo/DataFrame] and it would
> make a good fit
> * Comes with MIT licence
> * Depends only on `antlr4-runtime` and `slf4j`
> * It's API would fit nicely into a FreeMarker Template
> * It provides a DataFrame implementation and some basic transformations
> * It currently does not support temporal column types
> What I would like to implement is
> * Reading CSV & Excel into a DataFrame
> * Write a DataFrame to CSV
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