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Presenting quantitative data from different categories – Bar/columncharts
barchart is one of the most commonly used forms of presenting quantitative data. It is simple to create and to understand. It is best used when comparing data from different categories: e.q. public healthcare expenditure in the top 10 countries – and as 11th column your country. A typical columnchart looks like this:
Reading barcharts is simple: We usually have a few values – ordered as categories on the x or y axis (for column and barcharts respectively) in our example it’s the countries. Then we have the values expressed as bars (horizontal) or columns (vertical). The extent of the bars is the value.
As simple as it is there are a few rules to keep in mind:
- Don’t overload barcharts Although you can do multiple colours and pack two categories in there, if it’s too many categories it becomes confusing.
- Always label your axes whoever is looking at your graphs needs to know what the units are they are looking at.
- Start your values at 0. Most spreadsheet tools will automatically adjust the range: undo this and set it to 0 – this shows contrast in an appropriate scale! We’ll show you why this is important in the next module.
Walkthrough: Create a column chart for the top 10 countries.
So let’s create a column chart from our dataset. It’s not really good style to have too many different columns in there: the chart becomes very hard to read. So what we will do is to limit ourselves to the 10 countries with the highest healthcare expenditure. This is an arbitrary cutoff and you can look at all the countries as well. Doing so might help you discover something that’s hidden in the data.
- To do so, filter the World Bank dataset for a single year (e.g. 2009).
- Sort the filtered world bank data set by the column “Health care expenditure total per person (US$)” one of the columns we created in the last challenge. You can avoid having the first row being moved by going to View -> Freeze -> 1 row
- Select the top 10 countries (the first 11 rows including the header row) and copy it to another sheet. (For this press ctrl + c for copy and then insert a new sheet, press ctrl + v in the new sheet to paste).
- To select the data we are interested in, we can first select the name of the countries, then select the Health expenditure total per person while maintaining CTRL (CMD on a Mac) pressed. Another interesting option, especially if you have a small screen, is to move the second column to put it next to the first.
- To do so, click on the grey label to select it. Release the mouse then click and drag it until it is in position. Your column A should now be Country Names, Column B should be “healthcare expenditure per person total US$”. Your sheet should look like this:
- Now select the two columns of interest and then open chart... from the insert menu.
- One of the suggested charts should be a column chart
- Click on it and you will see a preview. Did you note the range on the y axis?
- It starts with 4000 so it looks like Belgium is only spending a fraction of Luxembourg’s spending on healthcare – let’s change this.
- Open the Customize tab and scroll down to “Axis” . Now select “Left Vertical” from the drop down.
- See the max and min boxes? Just enter 0 into the min and the range will start at 0. This way the contrast between the countries looks more realistic.
- Play around with the customizing settings. Try to remove and position the legend, change the colour of your bars etc.
- When you are done, click on Insert and your chart will be there.
- If you click on the chart you can move it around. Notice the triangle up right? It’s the option menu. Select Edit chart to change the settings of the chart. Can you change it to a bar chart?
Task: Create a column chart with other data from the World Bank sheet.
So now you know how to create a column chart – feel free to experiment with other types of chart and use the recipes in the Handbook to guide you. The following sections deal with when to pick a particular type of chart and what data it is suitable for. We cover the most common charts: line charts, choropleth maps and scatterplots. For all of these, you can find an accompanying howto recipe in the handbook.