I'm trying to work out how to calculate the length of a line to only 2 decimal places in QGIS. When I use the field calculator to create a new field, it doesn't matter what changes I make to the field type, field width or precision, I continually get the length to 13 decimal place.
In the latest dev QGIS version there is a new round function which you can use to control the number of decimal places:
Result: 1.10228762876525 -> 1.102
Load plugin : "Processing", Spatial data processing framework for QGIS
Select commandos in the menu bar "processing"
Type "field" in combobox
Select: "Processing algorithm: Refactor fields"
Set decimal positions in the fields
(If there are any items in the expression column are signed red just add "......" at begin and end (shapes don't like long column names with a space (so for example: column x coord has to be "x-coord")
Save to new file or temporally (so you can overwrite your excisting shape).