I want to create a map of India showing 30 districts that have the highest COVID-19 cases as of 31 December 2020 using QGIS. I marked the 30 districts and added the CSV file to this layer. I want to create a proportional symbol according to cumulative confirmed cases, but not with discrete values, but for specific ranges because the number of cumulative cases ranges from 55000 to 6 lakhs. I searched for the "Assistant' option in the 'size' section in the 'Properties' of the point. But in the input menu I am not able to give the source. It doesn't show anything for selection.So if I apply my changes, it is displaying graduated symbols not proportional symbol.
Check that the field is numeric. If it's a string, you can't use it.
You have 2 layers, a point layer an a table layer. The Table layer (20cities) has no geometry. The points layer probably has no attributes. You can either:
- Join the 2 layers, if necessary (harder)
- Just use the 20cities layer, as it has lat and long columns (that have not been imported as feature geometries). Set the geometry properly, by importing the table again, but make sure you set the 'long' column as the X field of the point feature geometry, and 'lat' as the Y field, as shown below (mine are Latitude and Longitude, which QGIS recognises automatically - you can change 'lat' and 'long' in your CSV file to Latitude and Longitude to see this automatically, or just manually select them).
To use size of the point based on a field you can only choose a field that contain number. When you do import your data from CSV QGIS choose the data type for every column. If the column contains anything that is not a number then all the colum would be considered as text.
You have a solution that will work without doing again the import csv process. You can click on the epsilon sign to open expression toolbox, it will help you make the formula to transform your data to integer type.
The expression toolbox have in the rigth side the function you can use and the decription. In the section
field and values you will find the list of the field in your dataset, double click on the field you want to use to add it in the left panel.
Then you can adapt the formula in the left panel to get this kind ofresult
try ( to_int ("MY_FIELD"),0)