Example - The potential impact of the L-line closure in New York City

Learn how to create buffers, intersects and explore with widgets using CARTO Builder.

You will need to import the following dataset/s into your account:

• New York subway stations: subway_nycstations_l. You can download it from here.
• New York subway lines: nyc_subway_lines. You can download it from here.
• New York block group census: nyc_block_group_census. You can download it from here.

In order to download them to your local machines, you are using CARTO SQL API behind the scenes.

Create a map

• Click on NEW MAP.
• Click on CONNECT DATASET.
• Drag and drop subway_nycstations_l.gpkg.
• Click on CONNECT DATASET.
• Click on Don't show me this again to avoid modals.
• You can rename the map title as “The L line and demographics” by double-clicking on it.

Layers

• Add new layers:
  • Click on ADD.
  • Clik on CONNECT DATASET.
  • Copy and paste this url https://builder-demo.carto.com/api/v2/sql?q=SELECT+*+FROM+nyc_subway_lines&format=gpkg&filename=nyc_subway_lines and click on SUBMIT.
  • Click on ADD LAYER.
  • Reapeat the previous steps but adding a dataset from this URL: https://builder-demo.carto.com/api/v2/sql?q=SELECT+*+FROM+nyc_block_group_census&format=gpkg&filename=nyc_block_group_census
• Now, by moving the layers using drag and drop we can change the order in which the layers are being displayed. We move subway_nycstations_l to the top and nyc_subway_lines in the second position. The layer nyc_block_group_census woudl stay at the bottom of the map.

• Click on one of the layers to show its components:
  • DATA tab: an overview of your table schema, from here you can also add widgets. If you want to have a look at your dataset, click the Data View icon, located on the bottom right of Builder when a map layer is selected.

• ANALYSIS
• STYLE
• POP-UP
• LEGEND

Have a look at the letter and number the layers card has (A, B or C). This would be very useful for adding widgets and analysis. Depending on the order in which you added your data, your layer letters could be different than the screenshots. In this example, subway stations were layer A, subway lines layer B, and block groups layer C.

Analysis

Filter by column value

• Go to the edit pane.
• Click layer nyc_subway_lines and then select the Analysis tab. Finally, click on the ADD ANALYSIS button in order to add the analysis.
• Select Filter by column value analysis.
• Click on ADD ANALYSIS.
• Set the parameters as follows:
  • COLUMN: route_id.
  • INPUT: L.
  • RESULT: show.
• Now click on APPLY to see the result of the filtering. This is the L subway line.

Areas of Influence analysis

• We will apply this analysis to the layer subway_nycstations_l. Go back to the LAYERS pane in Builder’s interface and click on 0 ANALYSES under subway_nycstations_l. Click on ANALYSIS, then on ADD ANALYSIS.
• Select the Create areas of influence analysis. Click ADD ANALYSIS.
• In the ANALYSIS tab of the layer, we have three sections:
  • Your workflow: Since this is the first analysis we’re adding to the subway_nycstations_l layer, node A, the analysis layer will be named node A1.
  • Create areas of influence:
    • Input: Should be the layer subway_nycstations_l, node A (A0).
    • Parameters: define the distance of the area of influence, the type of units, the radius and the boundaries. The boundaries can be Intact or Dissolved. Intact means our areas of influence polygons will keep their original polygon borders even if they overlap. On the other hand, if we choose the Dissolved option, overlapping areas of influence polygons will be merged. The result will be one big polygon whose shape corresponds to the outer edges of the original overlapping AOI polygons. Set the units to mi, set the radius to 1 and choose the Intact option for the BOUNDARIES parameter.
• After clicking APPLY, we should see this result: an area of influence of 1 mile around each subway station.

Intersect second layer analysis

• Go to the edit pane.
• Click layer nyc_block_group_census and then select the Analysis tab. Finally, click on the ADD ANALYSIS button in order to add the analysis.
• Select Intersect second layer analysis.
• In the ANALYIS tab of the layer, we have three sections:
  • Your workflow: Since this is the first analysis we’re adding to the nyc_block_group_census layer, node C, this analysis layer will be named node C1.
  • Aggregate intersection:
    • Base Layer: By default the base layer would be nyc_block_group_census.
    • Intersect Layer: select the result layer of the Area of Influence analysis A1
• After clicking APPLY, we should see this result:

Extract and reorder AOI analysis layer

Since we used our subway station layer as the input for the AOI analysis, the data appears as polygons. We want the AOI’s to be underneath the subway lines, and to extract the original subway station points for display.

• From the subway_stations_l layer, drag out the AOI sublayer and place it under the nyc_subway_lines layer
• This will create a new layer D, and you will see the subway stations drawn on top of the AOI and block group layers

Styling

• Go to the edit pane, click on the AOI layer D and select the STYLE tab. Set the Fill color to a grey with high opacity, and make the stroke grey also.

• Go to the edit pane, click on the nyc_block_group_census layer D and select the STYLE tab. Set the Fill color to a grey that blends with the basemap layer.

Widgets

• Go to the edit pane and click on the widgets tab.
• Click on ADD WIDGET button.
  • Under the CATEGORY tab, click on the check box of variables stop_name and ethnic_1st
  • Under the ‘HISTOGRAM’ tab, click on the check box of variables median_household_income and median_age
  • Under the ‘FORMULA’ tab, click on the check box of variable total_pop.
• Click on CONTINUE

Explore and style data with Widgets

• Click on the tear drop icon inside each widget to see the Auto-style feature.
• Filter the data by interacting with the category and histogram widgets.

Customize widgets

• Reorder widgets: From WIDGET tab, drag and drop them into your preferred order.
• Rename widgets: From WIDGET tab, rename each widget by clicking on its three blue dots and selecting the option to Rename.
• Formula widget calculation:
  • By default, the formula widget is calculating the average population. However, we want to see the sum of the total population within our map view.
  • Click on the three blue dots in the Total Population widget and select the option to ‘Edit’
  • In the OPERATION parameter, select sum.

Publish

• Click on SHARE.
• Set the map’s privacy to LINK or PUBLIC.
• Click on PUBLISH.
• Now you can share the map:
  • Link: https://public.carto.com/builder/eba0e807-f5a1-4d7d-9d80-56ebcdc7a2e2/embed
  • iframe: <iframe width="100%" height="520" frameborder="0" src="https://public.carto.com/builder/eba0e807-f5a1-4d7d-9d80-56ebcdc7a2e2/embed" allowfullscreen webkitallowfullscreen mozallowfullscreen oallowfullscreen msallowfullscreen></iframe>

Remember to update your map every time you make a change. To see those changes refresh your embed, or the web page where your map is hosted.