This article is the “H” part of a series of tips and formats (in alphabet order) to help you convey your data visualization messages in the best way possible. Starting with A for “Area Charts” and going all the way through W for “Word Clouds,” the pros and cons of each data visualization format will be explained and illustrated. This article starts with outlining the basics of Histograms:
Histograms were invented by Karl Pearson in 1911, who founded the department of university statistics at the University College London. They are a specialized version of column charts that group numbers and data into specific ranges. They are considered to be the most commonly used charts for demonstrating frequency distributions that show how often a value may occur in a data set.
The definition of a histogram is a:
“Visual representation of frequency distribution using bars whose widths represent intervals and whose areas are proportional to the corresponding frequencies.”
What this means is that the histogram is a version of a column chart that is really just a vertical bar chart version. The complexity involved in histograms is based on the fact that they typically deal with a range of quantities. Histograms are useful to display larger than normal data sets where there are data peaks as well as the statistical significance of the peaks and valleys.
A critical area of importance with histograms is in understanding the bin offset and the bin width. Each bar represents a variety of range values and you need to be aware that outliers could skew some of the bar ranges. Here is a simple histogram example:
Almost all individuals that design infographics are using one of the software packages. These offer the ability to tap into various date sources, glean the information, and display it in attractive ways that tell the story in a flow pattern so that it is understood well.
According to Small Business Trends, SAP Lumira Edge is one infographics software that can turn spreadsheets into infographics:
“You can create a variety of reports with simple infographics making the information easy to digest and understand. Data could be used to depict your average customer ‘life cycle’ or how sales patterns change with seasons and months of the year. It could also depict how sales responded during specific marketing campaigns and other initiatives.”
Here is a data visualization example of revenue by country and wine in the SAP Lumira software:
Isopleth maps are used to demonstrate a quantity of ranges and the data is displayed as a third dimension on the map. These are excellent for such topics as weather and radar data, temperature and rainfall maps as well as surface elevations. They typically have ranges that relate to similar patterns or colors that show changes over space. The ‘third dimension’ uses isopleths, which are a series of lines that connect points of equal value. Isopleth maps are different than choropleth maps as the data isn’t grouped to specifically predefined regions. These are often very complex and require large data sets for drawing accuracy. Here is an example of an isopleth map from the National Resources Conservation Soils website:
Line charts are really exactly as they sound: a type of chart that makes use of a series of points, known as ‘data points’ that connect by straight lines to display information. Connecting the points offer an easy visualization of data trends over a period of time.
Because line charts demonstrate trends in such an easy to understand way, multiple lines can be used on a single chart or a line can be fit atop data to convey a trend. In almost all cases, line charts make use of the x-axis for time and the y-axis for measurement.
Line charts have the ability to display decreases and increases and therefore overall trends and patterns in data in much easier ways than bar charts. Line charts are not as well received when showing specific data values, as the individual data segments are more difficult to perceive.
Here is an example of a basic line chart about Google PPC Sales v Overall Sales:
Image credit: Piermario