Visualizing 2016 presidential election data Apply predominant mapping, Z-Score

Transcription

1 Visualizing 2016 presidential election data Apply predominant mapping, Z-Score The 2016 presidential election in the US ended in a surprise victory for Republican candidate Donald Trump. GIS can offer a geographic perspective of the election results and can provide information to upcoming candidates concerning the where of the electoral contest. Build skills in these areas Visualizing election 2016 data using predominant mapping Visualizing election 2016 data with calculated Z-Score Using Arcade expressions What you need User, Publisher, or Administrator role in an ArcGIS organization Estimated time: over 1 hour Scenario Officials with both the Republican and the Democratic national committees have contracted you to provide them with a visual representation of the 2016 presidential election data. They want to geographically and mathematically display the election results in various ways. You have contracted to visualize the data using predominant mapping and a Z-Score. Finding and saving a map with 2016 population data 1. Sign in to ArcGIS Online organizational account. 2. Open Presidential Election On the top tab click Save As. 4. Save using the following metadata: Title: Presidential Election 2016_yourinitials. Tags: IGARC2_election_yourinitials. Summary: Presidential election results by county for Click SAVE MAP. Predominant category Category compares attributes that share a common subject and unit of measurement to see which has the highest value. Color shows the predominant category, and transparency shows the relative strength of the predominance. 1. Click the style icon under election Choose an attribute: % GOP. 3. Add attribute. 4. Choose an attribute % DEM. 5. Choose Predominant Category. Account required Click Options>>%GOP change to red. Click Options>>%DEM change to blue. 1

2 What does the map tell you about voting patterns in the 2016 presidential election? Category and size This type of predominant mapping is the same as predominant mapping by category except that it adds the additional variable of size, showing the sum of the categories. With predominant mapping by category and size, you can show three variables on the map. 1. Select Category and Size. 2. Click Counts and Amounts>>OPTIONS. 3. Click Specify size range. 4. Change the size to Min of 4 px and Max of 15 px. 5. Click OK. 6. Click DONE. 2

3 7. On the top tab, click Save As and save your map using the following metadata: Title: Presidential Election 2016 Predominance_yourinitials. Tags: IGARC2_election_results. Summary: Visualization of presidential election 2016 results using predominant mapping. 8. Click SAVE MAP. Z-Score A Z-Score is a numerical measurement of a value s relationship to the average in a group of values. If a Z-score is 0, it represents the score is identical to the average score. Z-Scores may also be positive or negative, with a positive value indicating the score is above the average and a negative score indicating it is below the average. Positive and negative scores also reveal the number of standard deviations the score is either above or below the average. One standard deviation either plus or minus accounts for about 68 percent of the people, in this case representing 68 percent of the people either voted Democratic or Republican. How to calculate Z-Score of %DEM Data you want to examine (in this case, % Dem). Subtract the average of % DEM from % DEM. Divide the subtraction figure by the standard deviation (% DEM average)/standard deviation. 3

4 1. Open Presidential Election On the top tab click Save As. 3. Save using the following metadata: Title: Presidential Election 2016 Z-Score_ yourinitials. Tags: IGARC2_electionZ_yourinitials. Summary: Presidential election results visualized by Z-Score. 4. Click SAVE MAP. Find the average and the standard deviation of %DEM calculate Z-Score 1. Right click election 2016 and open the attribute table. 2. Scroll right to the field % DEM. 3. Right-click on %DEM and click Statistics. 4. When you display the Statistics write down the Average and the Standard Deviation. 5. Click CLOSE. 6. Click the style icon under election Scroll down and select New Expression. 4

5 8. Click Edit and Name this Expression: Z-Score % DEM. 9. Click Save. 10. Type the following expression. Click Globals to display attributes. (($feature.dem_per) )/ Click Save. 12. Click Counts and Amounts (Color). 13. Click OK. 14. Click DONE. 15. Click Options and change the name of the layer to Z-Score %DEM. 16. Click OK. What does the Z-Score legend represent? How to calculate Z-Score of %GOP 1. Right click and copy the Z-Score %DEM. 2. Under Options rename the file Z-Score %GOP. Find the average and the standard deviation of %GOP calculate Z-Score 3. Open the attribute table and click %GOP. 4. Click Display Statistics. 5. Record the Average and the Standard Deviation. 6. Click Add attribute. 5

6 7. Select another New Expression and title it Z-Score GOP. 8. Type the following expression: (($feature.gop_per) )/ Click OK. 10. Click Counts and Amounts (Color). 11. Click OK. 12. Click DONE. You can visualize these by turning the layers on and off. 13. Click Save. In this exercise, you have visualized the presidential election data in 2016 by predominant mapping and Z-Score. You have made observations about the spatial distribution of the political parties voting preferences on your map. 6