4

I'm trying to create a visual map in QGIS 2.4 of the approximate distribution of journey origin points using a shapefile of UK postcode sectors, layer joined to a table with a column giving the number of journey origins in each sector. Using the Vector > Research Tools > Random Points menu tool, I can select the Input boundary layer and click the 'Use value from input field' radio button, but the pull-down menu to select the required field does not seem to work. If I then specify the Output Shapefile name and target location , I get an error message - "Errors: The following features IDs couldn't be calculated due to conversion error: 335, 335". To confirm, QGIS does display random points if I specify the density or a specific number of points using the first two 'Stratified Sampling' Designs for individual polygs.

  • Thanks Joseph, it worked! Worth pointing out to other novices struggling with this tool that the Layer Properties > Fields dialog box shows the value type. Adding a new column offered me the option of ensuring an Integer column was created and populated by cut'n'paste. Peter. – Peter A Nov 17 '15 at 16:49
6

When using the Random Points tool (from the toolbar: Vector > Research Tools > Random Points), the "Use value from input field" only accepts integer type fields.

As @PeterA suggested, field types can be seen from Layer Properties > Fields which can be used to create new fields and/or access the Field Calculator for additional functionality.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.