I am visualizing trade flows in QGIS. I am trying to make the line width of approximately 100 polylines be proportional to the associated value listed for each in the attribute table. Several posts show how to classify them into groups using Natural Jenks through the Layer Properties>>Style>>Graduated field. This is not what I'm looking for. I would like a code where I can say for example line width=value of attribute field. I may also want to do (value of attribute field)/100 or log(value of attribute field) so the scale of the line width is appropriate for the map.