For this project, we created a 2016 Presidential Election map using counties and the value-by-alpha method. To create this map, we used QGIS, a shape file of the US counties, and data from the election. The first step was for us to edit the data to make sure the FIPS codes had the leadings 0s. In addition, we also created a population ratio column. We then added this data to the shape file in QGIS and proceeded to edit the attributes to make sure some data had the proper decimal count and created the new attribute of total votes per county.The next step was to style the map which included adding a gradient fill with 7 shades to show democratic and republican votes. We followed this up with creating the alpha value layer and adjusted the values however we prefered. Next, we created a legend in the print composer along with the map and added additional text such as the map title and legend text.
This project was interesting because adding the value-by-alpha allowed us to visually map the population of counties, as well as the votes, without much distortion. Cartograms are a popular choice when creating presidential election maps but they result in the distortion of the units (often states) in order to visually represent population. Using the value-by-alpha allows us to add a layer over the map of votes which, depending on the votes per area, adds different values of transparency so that only certain counties are represented in full color while others blend more into the background. For my map, I wanted my map to show more color. In order to do this, I used the following formula in QGIS color_rgba(0,0,0,( scale_linear( "area" , 0.3,500,220,0))). In this formula, I chose the actual minimum of 0.3 for values and a maximum of 500 in order for more counties to be represented in brighter color.