Trouble with graduated symbols after joining shapefile with csv file

Question

I have successfully joined data from a csv file to a shapefile in QGIS but for some reason I am having trouble symbolizing my data. I want to use a graduated symbology however this option is not available for any of the columns for my joined table. I have tried saving as a new layer but this does not change the issue. Has anybody got any tips to get around this?

Answer 1

The problem most likely is that all CSV columns have been imported as text fields. Text cannot be used for graduated styles.

To fix this, you need a .csvt file for your CSV which specifies the data type of CSV columns explicitly. Basically, a .csvt file is a text file with only one line, e.g.

"Integer","Real","String"

For a CSV file with three columns. More info: http://underdark.wordpress.com/2011/03/07/how-to-specify-data-types-of-csv-columns-for-use-in-qgis/

You'll be able to verify if specifying data types worked, by checking the csv layer's "Fields" tab and the data types listed there.

Answer 2

I was trying to use the CSVT file too...

I got better results by simply saving a Libre Office spreadsheet to a DBF.

Then bring in the DBF into QGIS as a vector layer - and it will come in as a table.

The fields in the DBF in QGIS seem to auto-format quite nicely, whereas I couldn't get the CSV / CSVT file to work at all.

-mb