more parks.
Cypress Park, Elysian Valley Recreation Center Park, and Downey Playground are close to the river. Elyria Canyon Park, a little over three-quarters of a mile away (at its nearest edge), stretches the notion of proximity. Bear in mind that these measurements are straight-line distances, not the distance along streets.
11)Switch back to the Explore tool
12)Zoom to the City of Los Angeles bookmark.
Add a layer of census block groups
Another requirement for the new park is that it be located in a lower-income neighborhood. To symbolize an income attribute, you must add another layer to the map. (It’s not that income data isn’t reported at the census tract level, it’s just that your particular tracts layer doesn’t happen to include it.)
The same census folder that contains tracts.shp also has a shapefile dataset named block_groups.shp.
1)Open the Catalog pane and add the block_groups shapefile to the map from ParkSite > SourceData > census.
The new layer is added above the other layers. Like the tracts layer, the block_groups layer covers Los Angeles County. And like the census tracts, the block group polygons resemble a jigsaw puzzle. Block groups are another Census Bureau statistical unit: they’re smaller than tracts and nest inside them. We’ll talk more about census geography in lesson 2.
2)Open the attribute table of the block_groups layer and scroll across the attributes.
Most of these attribute names are cryptic. One of the last fields in the table is called MEDHINC_CY. For now, take it on faith that this acronym stands for median household income. Each block group value is a median value, in which half the households earn more than the median income value and half earn less.
3)Right-click on the MEDHINC_CY field name and Choose Statistics.
The statistics of the MEDHINC_CY for block_groups show a range from the lowest value of 0 to the highest of 200,001.
4)Close the table, histogram, and Chart Properties pane.
Symbolize census block groups by median household income
If you symbolize the block_groups layer with graduated colors, you won’t be able to evaluate income and population density at the same time. Instead, you’ll represent each block group’s median household income as a point drawn inside the block group polygon. The point sizes will be graduated according to the income value.
1)Using the Appearance tab, open the Symbology pane for the block_groups layer.
2)In the Symbology drop-down list, click Graduated Symbols.
3)In the Field drop-down list, click MEDHINC_CY.
4)Click the Classes drop-down arrow and click 3.
5)Replace the first value with 50000 and the middle value with 100000 and press Enter.
6)Click the Template symbol (underneath the Maximum size drop-down box) to open the Format Point Symbol pane.
7)Under Properties, click the Color button and change its color to Tourmaline Green.
8)Click Apply and then the back button at the top of the pane. This symbology sets the color and shape of the symbols that will be used to represent income values.
9)Click Background (to the right of Template) to open the Format Point Symbol pane again.
10)Change Color to No Color, if necessary, and then change the Outline color to No Color.
11)Click Apply and then the back button at the top of the pane.
This symbology makes the block group polygons themselves invisible. All you’ll see are the income dots spread around the map.
12)Change the Minimum size to 8.
13)Change the Maximum size to 24.
14)In the Label column, double-click on the first label (< 50000) to make it editable. Type Low, and press Enter.
15)Replace the second label with Medium. Press Enter.
16)Change the third label to High. Press Enter.
17)Close the Symbology pane.
At the present scale, the symbols overwhelm the map.
Set a visibility range for the block_ groups layer
Earlier, you set a maximum scale value for the World Boundaries and Places layer. Here, you’ll set a minimum value for the block_groups layer.
1)With the block_groups layer selected in the Contents pane, open the Appearance ribbon.
2)Click in the Out Beyond box and type 100000. Press Enter.
The symbols disappear from the map. In the Contents pane, the layer’s dimmed check box indicates that the layer is turned on but is not visible at the current map scale.
3)Zoom to the Dodger Stadium bookmark.
4)Click the Fixed Zoom Out button a couple of times until some of the Medium and High symbols begin to appear.
5)Turn the tracts layer back on.
Now you can start to get a general sense of household income and population density along the river, and look at these variables in relation to park locations.
Search for likely park areas
Clearly, you’re taking an incomplete initial look at a complex problem. You haven’t considered all the requirements (for example, the presence of children). You’re not making any exact measurements of distance. Your data classifications are casual: you don’t yet have a good reason to say what values should count as high population density or low median household income in the context of your project. Nevertheless, you can form some meaningful impressions. You won’t be able to say of an area that a park should definitely go there, but you might be able to identify likely and unlikely areas. Later, it will be interesting to see how well these impressions are borne out by analysis.
1)In the Map Scale box at the bottom of the map pane, highlight the current value. Type 40000, and press Enter.
2)Pan south to where the river crosses the city boundary.
You’ll
