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Hi Lionel.Originally Posted by Lionelgee
Not sure where the term 'heat map' comes from unless it is a colloquial term applied to maps that use varying shades of red to represent different temperatures in different regions. Choropleth is really about the use of the entire colour spectrum to represent data. In some situations shades of one colour might suffice. Choice is up to the user or dictated by the data.
An AI search comes up with (apparently) free mapping programs like QGIS, SAGA GIS, ILWIS, DIVA GIS, FALCONVIEW - I haven't used any of them.
I'm only familiar with linking spreadsheet data and map data together using a mapping program. I don't now if advances in Excel allow it to replace the mapping program.
About 18 years ago, in a past life, I used MapInfo to 'join' map files and Excel spreadsheets together to create choropleth maps.
To start with, simply put, you need (1) a map file, (2) an empty spreadsheet and (3) a mapping program aka a GIS program.. The first column of numbers, unique numbers, in your map file is copied to the first column in your spreadsheet. You load the remaining spreadsheet columns with your research data, as many columns as needed, arranged against the relevant unique number. The mapping program uses the list of numbers, unique numbers, to tie together each map region with the spreadsheet data that belongs to that map region.
The data, now tied to a region, is colour coded by a choropleth process, then presented as a finished map. The choroplething, or colour coding, is done in the mapping program - the data breaks for scaling and colour arrangement is up to you. As you have indicated, if there is no data for a region then the region could be white unless you make instances of 'no data' the first pale shade from your scale.
There will be as many lines in your spreadsheet as you have geographic regions, ie 20 regions = 20 lines.
If you collected 5 types of data from 20 regions then the spreadsheet will be 20 lines deep by 6 columns wide.
In your spreadsheet you will have your uniquely numbered geographic regions (column 1) number of sheep in each region (column 2) number of cattle in each region (column 3) weight of fish caught in each region (column 4) number of people in each region (column 5) number of barbecues in each region (column 6).
To create a map you will see inside the mapping program all the data headings that were in your spreadsheet. In your first set of maps you might want to choropleth the population by geography first, so you choose column 1 and 5. Next set of maps, number of cattle by geography, so you choose 1 and 3. Barbecues by region 1 and 6 etc.. You could devise a map that has both number of people and number of cattle by geographic region, but you generally do not do that - such a map for example could be coloured to represent the cattle, with black numbers in each region representing the number of people. Usually a choropleth map represents all the geography regions against one data type at a time. If you want to compare more than two data types against geography you should resort to graphs and data tables. Choropleths are for simple visual representations, as are the frowned upon pie graphs.
Again inside the mapping program, you set the data breaks and corresponding colour(s) that you want - this will be the scale on your map. Sometimes natural breaks in the data may dictate how the scale is devised. Usually keep the breaks to a small number ie less than 100 sheep, less than 500 sheep, less than 1000 sheep, less than 5000 sheep...less than 10000 sheep, greater than 20,000 sheep. If you had a zillion sheep and a zillion different shades of one colour or a zillion of all colours, then no one is going to be able to tell one subtle shade from another, the map would be unreadable. The fewer number of data breaks in your scale the better the colour contrast.
May be wrong, but you may be able to get ABS map files from their website, like State/Local Area (SLA)/Collection Districts (CD)/sub-CD. Oherwise you need to buy a map file or you make your own in the mapping software. Organisations often have their own purpose built maps or they manipulate (redistrict) ABS maps to get an approximation of their geography that mainly meets their needs. Redistricting is often done on a consultancy basis by the organisation that owns the maps - not because the agency does not want to give you the map, but because many researchers don't know how to redistrict maps. Organisations often want to compare their own data with ABS data on population, income, occupation etc so it pays to use an ABS map or some manipulated version of an ABS map.
If the 'specific group of people' you refer to are of Aboriginal or Torres Strait Islander descent then ABS has covered that in Indigenous Community Profiles, from memory free from their website. If you are talking about country of birth groupings then you may find ABS Census profiles for free on their website. Same with occupation groupings, income groupings etc. ABS usually releases the commonly demanded data as publications, for free. You will usually pay where you want something not commonly required, or you want a variation on an already released publication.
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