PORTAL USER GUIDE
A Choropleth (from the Greek χώρο (“choro” = “area/region”) + πλήθος (“pleth” = “multitude”)) is likely to be the most common kind of map visualisation that AURIN users will make with the data that they access. It is a thematic map in which areas are shaded or patterned in proportion to the measurement of a variable being displayed on the map, such as population density or average income.
For this worked example, we will look at the distribution of mortgage costs across Tasmania.
To do this:
- Select Tasmania (ste/6) as your area.
- Select the ABS – Data by Region – Family & Community (SA2) 2011 – 2016 as your dataset with the following variables:
- SA2 Code 2016
- SA2 Name 2016
- Year: 2016 (select from Filter Value)
- Household Stress: Households with Mortgage Repayments Greater Than or Equal To 30% of Household Income %
Once you have added these datasets, you are ready to create your choropleth – follow the Inputs tab above to see how to do this.
Now that you have added your datasets you are ready to create a choropleth map.
To do this, select the Choropleth tool (Interactive Maps & Charts → Mapping Areas/Polygons → Choropleth) in the Visualise pane. This will bring up a range of fields that need to be populated. Enter your parameters as you see them below and click the Add button.
- Select a dataset: Here you can choose which of the datasets you would like to display as a map. Select ABS – Data by Region – Family & Community (SA2) 2011 – 2016
- Select an attribute: This is the field that you want to map. If you want your map to make sense, and actually display the variable you are interested in, it is important to make sure you have selected the right attribute to map together with right classifier. Select Household Stress: Households with Mortgage Repayments Greater Than or Equal To 30% of Household Income %
- Select a classifier: Here we define how we break up our range of values in the attribute. For an attribute that is numerical in format (either an integer or a decimal), the default setting for this field is Jenks (Natural Breaks), which breaks your data up into intuitive groups based on the shape of the distribution of values. You can select Quantiles or Equal Intervals. If your attribute is categorical – that is, if it is a description or a word (such as a land-use zone, or a name, or any kind of “string”) then the parameter will automatically set to Pre-classified. Select Jenks (Natural Breaks).
- Number of Classes: This slider allows you to define the number of breaks in your data (minimum of 3, maximum of 12). The number that you choose should depend on the distribution of your values, the number of data points (areas) and the information that you are trying to portray with your data. Select 5.
- Select a palette type: Here you can choose the type of colour scheme for your data – Sequential, which shifts from a shade of one colour to another; Qualitative, where the colours are unique along the palette (used for Pre-classified) ; and Diverging, where colours shift to two colours from a central point along a natural spectrum. Select Sequential.
- Palette: This allows you to choose the actual colours of your palette (you can switch the ends of the palette around by clicking the Reverse Palette box at the bottom of the box. AURIN uses colours generated by Colour Brewer. Select Yellow – Green – Blue (YlGnBu).
- Default Opacity: This slider allows you to define how opaque your map is over the base map. 0.00 indicates completely transparent, 1.00 indicates completely opaque. Select 1.00.
- Hover Opacity: This slider allows you to define how opaque you want specific areas to be when you hover over them with a mouse, with the same values as for Default Opacity. Select 0.85.
- Stroke/Line Opacity: This slider allows you to define how opaque your polygon borders will be, with the same values as the Default and Hover Opacity. Select 1.00.
- Reverse Palette: This reverses the sequence of colours in our colour palette. Untick this box.
- Hide Null Values: This hides null values from appearing as a category on the map. Untick this box.
- Save Visualisation as: The default for this field is “[Attribute] -1” It’s a good idea to change the name of this to something that reflects the data, particularly if you plan on having multiple choropleth maps from different datasets. The name that you choose here will also be displayed in the legend automatically generated for your map. Type Percentage of Households spending 30% or more of income on a mortgage.
Once you have selected your parameters click Add Interactive Maps & Charts.
Once you click Add on the input box, a map will appear automatically in your viewer which should look something like the map shown below. If you hover over any of the areas, the value for the attribute that you have mapped will show, as well as which group in the legend that specific area belongs to.
Hovering over a certain class within the legend will also bring up all of the areas that belong to that specific class (shown below)
Alternatively, if you have a table open while a map visualisation is visible, hovering over an entry in the table will bring up the corresponding area on the map and vice versa. The tables and the maps do not need to be from the same dataset: if they correspond to the same geographic areas (i.e. 2016 Census SA2s from Tasmania), the interaction between the table and the map will show