# Histograms in Geography

## What is a histogram?

A histogram appears similar to a bar chart. However, there are key differences between the two. Histograms are used to present continuous data (a bar chart is used to present discrete data).

## When is using a histogram appropriate?

Histograms are ideal for presenting continuous data. Continuous data is data that falls in a continuous sequence e.g. time, distance and temperature. An example of this would be after counting pedestrians at 15-minute intervals over 2 hours, a histogram could be used to present the results.

## Creating a histogram

Creating a histogram is relatively simple. In this example, we are going to produce a histogram to show the results of a pedestrian count completed at 15-minute intervals over a continuous period of time. Students have collected raw data that shows the number of pedestrians that passed them during 15-minute intervals over two hours.

• 8-8.15 am – 120
• 8.15-8.30 am – 156
• 8.30-8.45 am – 176
• 8.45-9 am – 167
• 9-9.15 am – 101
• 9.15-9.30 am – 134
• 9.30-9.45 am – 123
• 9.45-10 am –  132

Step 1 – Decide on the scale of the X-axis

Decide on an appropriate scale on the X-axis for the bars. The bars should be the same width and there should be no gaps between the bars.

Step 2 – Decide on the scale of the Y-axis

Decide on a suitable scale for the Y-axis for the number of pedestrians. The scale should be spaced evenly and allow for the highest number in the data set to be included.

Step 3 – Create the histogram

Accurately draw the bars for each piece of data. As the data is continuous, each bar should be shaded in the same colour

Step 4 – Finish your graph

Include a title and label each axis.

To read a bar chart, read along the x-axis (bottom) to find the bar you want to read. Go to the top of the bar and read across to the scale on the y-axis to work out the value. Using a ruler can help with this.

The data below shows equal class intervals of vehicle flow for a continuous timescale. Present the data as a histogram.

3-3.30pm = 123
3.30-4pm = 160
4-4.30pm = 134
4.30-5pm = 206
5-5.30pm = 280
5.30-6pm = 305
6-6.30pm = 245

Of course, histograms are much easier to create using spreadsheet software such as Excel and Google Sheets. Download an example using the data shown above.