QGIS CSV & Delimited text Issues

Originally posted on xyHt Magazine 10th August 2016

Last month I was at the Maptime in Southampton (UK), helping QGIS new users how to join tables and map EU referendum maps when I came across an issue with something on QGIS I hadn’t spotted in the last *ahem* years of using it.

When you drag and drop txt, csv or other delimited files into QGIS the fields automatically get converted to text format. No, I’m not making it up and it caused a lot of embarrassment when I was giving my demonstration.

 

draganddrop fields
By dragging and dropping the csv file, you can see that the field type is solely “String”

 

This isn’t written to complain about QGIS but to notify others who are wondering why their joins aren’t working or why their interpolation can’t pick up the value field….You QGIS guys are going to say “why haven’t I raised this as an issue?”, well, firstly read Nyall Dawsons blog post on QGIS issues , secondly I tried to…..it turns out that trying to get access to submit issues has changed and even though I’ve asked for help to get access I’ve been waiting 1 month for response to request.

So…why does it happen?

If you add the file through the “add delimited file” button, none of this is an issue, this is due to the was that the software is written When the file is “dragged & dropped”, the software relies on OGR to add it as a comprehensible layer and this just renders all the fields as text (at present August 2016).

Add layer fields e2e
By adding the csv file using the add layer method, you can see the fields are brought in correctly

Why is it an issue?

If you are joining tables and aren’t aware of the issue, you drag and drop a table with a list of numerical values in, and then can’t join it to a spatial data with values in as you can’t join text to numbers. This could also cause issues with interpolation (reading of a value field) and also generation of points which need classification based on numbers.

Getting it fixed…

This is where things get a little tricky, as I don’t think it is entirely a QGIS issue and more related to the code which QGIS uses to parse the information, so until OGR update their code, it might be a bit of a wait.

 

Dragons8mycat

 

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s