How do you join the geometries that come with the topojson file with the attributes that come with a csv file? I was able to do this through QGIS by using the join feature and using the name of the counties to join them both. I also was able to do this through including NAME in the code above so observable knows the connection between the cvs file and the topojson file.

Which colors are used for bivariate mapping on Observable? Explain how to add a new bivariate color scheme. Colors that are able represent high high, high medium, high low and so on so they have to be able to mix with each other well and represent those values in an easy way for the reader which can be very different. Basically, there are a set of colors that are used for a bivariate map that are found outside of the observable website that are used (like using color brewer for the color schemes on other assignments). How you an add new color scheme is by adding a new name: and then colors: (list the HEX code for the colors here) and that will be added to the drop down list above.

How do you create a legend? How do you position the legend so it is not hidden behind the map? You create a legend by using this code above that includes everything from the arrows on the legend to the colors and to the title of the legend. I was able to position the legend so it was not hidden behind the map by adjusting the code named height = and the width = (which adjusts the map) and was able to resize the map so both the map and the legend can be shown. I did not move the legend itself because I liked the placement it was already in.

How do the values get displayed when you hover over each polygon? Under the svg.append("g") the line of code: .data(topojson.feature(polygons, polygons.objects.countiesandcropiowa).features) was added which took the values from the counties and crop iowa cvs and placed them on appropriated polygon.