Working With Census Data
You will do some basic analysis using the census data you downloaded.
- You will explore the population distribution in the province
- Explore employment rates across the dissemination areas
To accomplish these tasks, you will do a few tabular calculations and also create cartographic representations. You will email me a copy of one of these.
Set up your data for analysis
Last week you performed a join on a shapefile and the tabular data from a csv. This join between the two data files is temporary. That is to say, the tabular data is not permanently linked with the shapefile.
- To add the tabular data to the shapefile, export the shapefile with the join to create a new shapefile called BCDAPop
- Open the attribute table for BCDAPop. You may find that the fields with the census data have very similar names. You need to correct this.
- On BCDAPop > Right Click >> Properties >> Fields
- Click the Toggle Editing Mode button (in the top bar of the Fields window)
- Rename the fields appropriately. You will need to look at the shapefile with the join to make sure the names you assign correspond to the correct columns. To edit a field name, double click in it.
At this point you should have a shapefile, BCDAPop with the population and labor related attributes. These attributes should be labelled appropriately and intuitively so you can quickly tell what each column represents. If you don’t have these things in place, please don’t proceed to the next steps.
Understanding your data
What is the interpretation of each column? For example, what does the column for the total population represent and how is that different from the column representing the population 15yrs and over? How about the columns of those in the labor force?
- Change the projection of your data to a commonly used projection for BC. There are different ways this can be done, but for our purposes, you will change the map’s coordinate reference system (CRS).
- From the Main Toolbar > Project >> Properties >> CRS
- In the filter field search for 6653.
- Select NAD83/UTM Zone 10 EPSG:6653 and Click OK
- Calculate the area of each DA polygon
- Open the Attribute Table >> Open Field Calculator
- Select Create new field
- Output field name: area_sqm
- Output field type: Decimal
- Under the Expression tab type: $area
- Click OK
- The area you have calculated is in square meters, you should convert it to square KMs.
- Using the field calculator, create a new field called area_sqkm and calculate the area in Square Kilometers. Use the values in the field you created in the previous step (area_sqm/1000000)
- Now calculate the population density per dissemination area. You should be able to this without much assistance. Use the total population column and the column with the area in square kilometers.
- Which dissemination area ID has the highest population density?
- In a new field create a ratio of those who are employed to the population 15yrs and over.
- From the map view which areas have the highest ratios of those who are employed?
- Hint: Properties > Symbology > Graduated Colors
- Finally create a map showing two classes where one class is for Dissemination areas with a population density between 0-1. All the other values should be in the other class.
- Export it as a PDF (remember Print Composer) and email it to me: firstname.lastname@example.org
- It doesn’t have to be pretty. I am not going to grade it. I just want to see your finished hand work.
- Safe your project we will use it again.