Create a new column with an expression

[microfuge]

I have tabular data and I want to add an extra column which is some operations over existing columns. E.g `str(c2) + “__” + str(c3)` . I don’t want awk as the step for new users.

I would be grateful for a tool which can do this without multiple steps.

[jennaj]

Hi @microfuge

I’m guessing that you have already tried with the Compute on rows tool but are getting an error with Invalid expression: at the start, yes?

The issue is that the underscore character cannot be passed directly as it isn’t a whitelisted character that passes through the wrapper’s QA sanitation.

tools/column_maker/column_maker.py

Syntax

Using the Unicode value instead can work through the Python interpreter.

• Unicode Lookup: convert special characters

Specifically for your use case, this fails

c2 + “__” + c3

Instead, try using this

c2 + chr(95) + c3
c2 + chr(95) + chr(95) + c3

Please give this a try and let us know what happens!

Example details

• https://usegalaxy.org/u/jen-galaxyproject/h/demo-writing-underscores-with-compute-on-rows
• Compute on rows ( at UseGalaxy.org)

[microfuge]

Thanks @jennaj . That worked. Although for new users this solution is a bit less straightforward. An editable spreadsheet would be great in Galaxy :).

[jennaj]

Great, glad that helped!

For editing files directly, have you seen the Editor tool under Visualizations?

This is very basic editing function and error prone but also really useful!

@jennaj

And, Galaxy also has a regular text editor – how well that would work depends on how large your file is – and it would be very easy to introduce a problem! But you can experiment.

• Screenshot of how to find the text editor. Click on the visualize icon within an expanded dataset, then search for “editor” in the listing.

  

The process goes something like this

0. Expand the target dataset
1. Visualize icon
2. Search for the Editor
3. Type in new content into the file
4. Click on export*
5. The modified output is written as a new distinct dataset in the history
6. Repeat as needed!
7. Double check with Tabulator and consider using Convert delimiters to TAB after

*export is really pale (on purpose!) unless hovered over, so I’ll share a screenshot for where to look!