E has coordinates 1, 1 , so it is plotted 1 unit to the right and 1 unit up, that is, opposite 1 on the x-axis and opposite 1 on the y-axis.
F has coordinates — 2, — 1 , so F is plotted opposite — 2 on the x-axis and opposite — 1 on the y-axis. The coordinates of G are 1, — 3 so G is plotted opposite 1 on the x-axis and opposite - 3 on the y-axis.
The coordinates of H are — 2, 3 so H is plotted opposite — 2 on the x-axis and opposite 3 on the y-axis. In the examples so far, all the coordinates were whole numbers and the scales were also marked at whole unit intervals. It is possible to plot points that have decimal coordinates such as 1. In the graph below, each unit along the axes has been divided into ten, so each gray line represents a tenth of a whole unit, or 0.
The point A has coordinates 1. B is plotted at the point which is 3 intervals to the left of the origin on the horizontal scale and 4 intervals past the 1 mark on the vertical scale, i. So the coordinates of B are — 0. You have seen that, provided you have both an x- and a y-coordinate, you can plot a point on a chart.
So if a set of data consists of pairs of data values, then the data can be plotted on a graph. So in week 34, the woman had a weight of lb. This can be written as 34, and plotted on a graph in the same way as the earlier examples. If we take the x-coordinate of each point as the week of pregnancy and the y-coordinate as the weight in lb, then points can be plotted at 34, , 36, , 38, , and 40, to represent this set of data.
In the examples considered so far, the scales on both axes have been provided for you. The scales have been the same on both axes, and they have both started at zero. However, this is not always necessary. Scales are usually chosen to illustrate the data clearly, making good use of the graph paper and using a scale that is easy to interpret.
In the example of weight during pregnancy, if the scales started at 0, all the points would be plotted in the top right-hand corner and would be difficult to read. The y-values range from to , and the x-values start at 34 and end at So, the difference between the lowest and highest y-coordinate is 7, and the difference in the x-coordinates is 6.
A clearer way of presenting this data would be to use a scale on the x-axis that starts at 30 and ends at 42, and a scale on the y-axis that starts at and ends at Using these scales, the points could be plotted as follows. When the scales have been marked on the axes, remember to label the axes to show what is being measured, and include the units.
Then plot the points and, if appropriate, join them with a line or smooth curve. You may also use an object with a straight edge, such as a ruler or piece of paper, and hold it up to your monitor to help visualize where certain points appear in relation to the axis.
For example, to estimate her weight at 35 weeks, first find 35 on the horizontal axis. Then from this point, draw a line parallel to the vertical axis, until the line meets the curve at point P. From P , draw a line horizontally, to meet the vertical axis. Read off this value: here, it is about Determining values between the plotted points is known as interpolation.
Then draw a line horizontally from this point to intersect the vertical axis. This value is approximately Draw a horizontal line to meet the curve. Then draw a line vertically down to meet the horizontal axis. Read off the value: it is just over 34 weeks.
For example, if the baby had still not been born after 41 weeks, then you might estimate that the mother would weigh about Trying to estimate the coordinates of points on the graph that lie outside the plotted points is known as extrapolation. It can sometimes be used to find values that are close to the plotted data set, if you are confident that the graph continues in a similar manner.
However, you do need to be cautious: we cannot be certain that trends shown in graphs will continue. The graph can also be used to determine the overall trend in the data—how one value is changing with the other. It shows that she gained weight quite rapidly between weeks 34 and 36, but from week 36 to week 40 she gained less.
The following data values were collected on the circumferences and diameters of various circular objects. All of the measurements are in inches. Draw a straight line through the points. Remember to refer back to the summary of how to draw a graph so that you include all the detail needed. In particular look at the data you are given carefully before you decide what scale to use for the x- and y-axes.
Note the title and labeling of the axes. You may have used a different scale from us if you had different graph paper. This is fine as long as it makes best use of the paper and is easy to read from. From this point, draw a vertical line to meet the graph. Then draw a horizontal line across to the vertical axis and read off the value.
The circumference of a circle of diameter 15 in. From this point, draw a line horizontally across to the graph, then vertically down to the horizontal axis. The point where this line crosses the horizontal axis gives the diameter of a circle whose circumference is 30 inches. It is about 9. This is calculated by dividing the rise of the line by corresponding run of the line as shown below.
In the next section we will look at bar charts and the different ways that these can be drawn depending on the data that you have and what you want to show. Earlier, you saw data from the Irish Tourism Fact Card presented in tables. Information can also be illustrated in bar charts. The chart below is also from the Tourism Fact Card and shows the numbers of visitors participating in different activities.
In a bar chart, the length of each bar represents the number in that category. The shortest bar is for cruising, indicating that this was the least popular activity of those listed. On this bar chart, the values represented by the bars have been marked directly on the chart. If the values had not been marked on the bars, they could have been estimated by drawing a line from the end of the bar and seeing where it intersected the horizontal axis. For example, the end of the cycling bar is level with the marked on the horizontal scale as shown by the dashed line , so approximately , visitors went cycling.
Because the bars on this chart are horizontal, the chart is known as a horizontal bar chart. Bar charts can also be drawn with the bars vertical. Note that in a bar chart, each bar has the same width, and since the bars represent different and unrelated categories, the bars do not touch each other and are separated by gaps.
There is no label on the horizontal axis, which you would normally expect to complete a bar chart. The same basic guidelines apply to drawing a bar chart as they do to drawing a graph, so bear these in mind when completing this activity. In an earlier activity, you created the following table showing information about hotel guests. Use the table to draw a vertical bar chart to show the total number of guests in each of the nationality categories.
Mark the nationality categories on the horizontal axis and the number of guests on the vertical axis. Notice how this bar chart stresses the total number of tourists in each category. You can see easily that there were more tourists from Ireland than any of the other groups. If you wished to show how the totals were broken down into the different age groups, you could split each bar into three different sections where the length of each section represented the number of guests in that age group.
The resulting component bar chart is shown below. Notice that a key or legend has been added to the graph to explain the shading for the different categories. When you read a component bar chart, you need to find the height of the relevant section.
For instance, the top of the section representing British adults is opposite the 10 on the vertical scale. The bottom of that section is opposite the 4. So the number of British adults is 10 minus four equals six.
Draw the component bar chart for yourself from the hotel data and compare it to that shown above when you have finished. Another way of displaying the totals would be to split each bar into two, one representing the number of males and the other the number of females in each category. To enable these numbers to be compared directly, the bars representing males and females can be placed next to each other as shown below. This is an example of a comparative bar chart. Notice how all these charts followed the same format with the title and source clearly labeled and the axes and scales clearly marked, but they emphasized different aspects of the data.
When you are displaying data in a graphical form, it is important to choose a chart or graph that stresses the main points as simply as possible, so that your reader can understand your chart quickly and easily. The tourist market bar charts display how many items in this case, guests there are in each category.
How many times an item occurs is known as the frequency. Charts that display frequencies are also known as frequency diagrams. You may have heard of Florence Nightingale as a pioneer in nursing practice, but did you know how important data was to her and that she also invented the pie chart? This brief video will give you an insight into her work:. Although bar charts are useful to display numbers and percentages, sometimes you may wish to stress how different components contribute to the whole.
Pie charts are often used where you want to compare different proportions in the data set. The area of each slice or sector of the pie represents the proportion in that particular category. For example, the pie chart below illustrates the favorite type of exercise for a group of people.
This pie chart shows the percentages for each category, so you can read these off directly. Notice, however, that the source of the data has not been stated, so you do not know where it came from or how many people were interviewed. It is important to consider both these points. If, for example, it was a small sample, you may not wish to rely on the results to generalize to a larger group.
Sometimes the percentages are not marked on the chart. So, the proportions can then be roughly estimated by eye. For example, the pie chart below illustrates how employees in a particular company travel to work. It is important to remember that pie charts are useful only for comparing proportions, looking at parts of a whole. If you are interested in other aspects such as trends or frequencies, then other graphs or charts may be more appropriate.
If necessary—provided the pie chart has been drawn accurately—you can also work out the percentages by measuring the angle at the center of the pie for each sector, using a protractor. Pie charts are often used to give an overall impression rather than detailed information, so on many occasions a rough estimate will suffice. If you have a protractor you can print off the pie chart and work out the proportions for the other sectors.
You may need to extend the lines of the circles for each sector so that you can measure them properly with the protractor. Take time to make sure that you understand what the graph is telling you.
You have also created graphs by hand. You may prefer to use a computer to draw your graphs and charts. There are many exciting ways to present data, but the important points listed below still apply whether you are drawing graphs by hand or by using software. Look out for real-life graphs and charts in newspapers, magazines, on television, or on the Internet. Do these graphs follow the guidelines? Can you understand what the graphs are illustrating? The graph below shows the monthly heating bills of a house, before and after attic insulation was installed.
Was just one house used in the survey, or were many houses used? The axes are labeled but the scales are not marked. Then the apparent drop in the bill after insulation would be negligible. No scale is marked on the horizontal axis, either. In fact, the data was collected from November to September, so the horizontal scale should have indicated this. However, without the scale on the vertical axis, it is impossible to say what kind of drop this is.
From the data, the drop in the monthly heating cost occurred in the May bill just as the weather was warming up for the summer. The reduced bills could simply be due to less heating being used in the summer.
The last activity illustrated an important point: when you are comparing two sets of data, you need to compare like with like. You would expect the bills for the summer to be less than those in the winter anyway, regardless of the presence or absence of attic insulation. It would be more appropriate to consider the amount of energy used for heating over two periods with similar weather.
Alternatively, you could compare two similar groups of houses, one group with the insulation and the other without, over the same period of time.
So although graphs and charts are very useful, it is important to read them critically, checking that all the information you need to interpret them is provided. Another important point to note when interpreting a graph is that if the graph appears to show an association between two quantities, it does not prove that one has caused the other. For example, suppose the number of students in a town registering in a math course rose from year to year and the number of burglaries in the town also rose.
Does this mean that the math students have committed the burglaries? No, of course not! Both rises may be linked to some other factor such as the number of people who have recently moved into the town.
However in other situations, it may be much more tempting to suggest that one thing has caused another—for example, if the number of cancer cases are higher around nuclear power plants than elsewhere. In order to establish cause and effect, very large statistical surveys and analyses have to be carried out. This short video clip describes how the link between smoking and lung cancer was investigated. In this unit, you have seen how to visualize data as graphs, bar charts, and pie charts.
However, there are many other exciting ways of presenting data, including interactive displays. As an example, watch the video clip below. It summarizes years of world development for countries in just four minutes! Chart labels, headings, and annotations should be used to explicitly state the things you want your readers to take away from your chart, to eliminate the possibility of misinterpretation.
When labeling lines, bars, or points, try to avoid relying on a separate legend. Link to your data source at the bottom of your infographic in small type less than 10 pt size. Pro Tip: Use a link shortener to make your link easier to access.
For more complex charts, choose one key color to distinguish more important values from less important values and use gray to attenuate the data that you want to be less of a focus. Have a time series? Order it with the earliest data point on the left and the latest data point on the right. Have a pie chart? Representing categories that have no natural order? Consider ranking them from largest to smallest. Finally, when visualizing data in an infographic, I urge you to exercise restraint.
Infographic data must be easy to understand at a glance. If this means manipulating your data by removing points, grouping points, or by looking at shorter spans of time , take time to consider the tradeoff between readability and data accuracy. Try to reduce your dataset down to its most essential pieces without introducing inaccuracy or skewing your data. Contrasting a single bright color with muted greys can help your readers make sense of even hundreds of data points:.
A good way to make sure that your chart is simple enough? Have a friend look it over, and resist the urge to explain it to them. Alternatively, do a squint test. If not, simplify your charts a little more. The power of well-presented data should not be underestimated, and the right chart can make all the difference.
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Courses Develop your design knowledge. Infographics for beginners Become an Infographic Pro. Pie charts are not meant to compare individual sections to each other or to represent exact values you should use a bar chart for that. When possible, avoid pie charts and donuts. I would not recommend using stacked donut charts at all!
I mean, like, never! You might think that you could use a stacked donut to present composition, while allowing some comparison with an emphasis on composition , but it would perform badly for both. Use stacked column charts instead. For those of you who still feel sentimental about the old PowerPoint Pie charts, and want to keep using them, there are some things to keep in mind.
Scatter charts are primarily used for correlation and distribution analysis. Scatter charts can also show the data distribution or clustering trends and help you spot anomalies or outliers. A bubble chart is a great option if you need to add another dimension to a scatter plot chart.
Scatter plots compare two values, but you can add bubble size as the third variable and thus enable comparison. If the bubbles are very similar in size, use labels. A good example of a bubble chart would be a graph showing marketing expenditures vs. A standard scatter plot might show a positive correlation for marketing costs and revenue obviously , when a bubble chart could reveal that an increase in marketing costs is chewing on profits. Map charts are good for giving your numbers a geographical context to quickly spot best and worst performing areas, trends, and outliers.
If you have any kind of location data like coordinates, country names, state names or abbreviations, or addresses, you can plot related data on a map. A good example would be website visitors by country, state, or city, or product sales by state, region or city.
Gantt charts were adapted by Karol Adamiecki in But the name comes from Henry Gantt who independently adapted this bar chart type much later, in the s. Gantt charts are good for planning and scheduling projects. Gantt charts are essentially project maps, illustrating what needs to be done, in what order, and by what deadline. Showcasing data may seem simple in the age of PowerPoint, Prezi, Canva, Visme, Haiku Deck, and other nonsensically named technological platforms.
What could be a bigger chart fail than the chart itself being rendered useless? How you present data can double — or decimate — its impact, so take note of these seven ways to ensure that your data is doing its job. What is readable on your laptop may be far less so when projected on a screen. In comic book terms, you are Wonder Woman, and data is your magic lasso — a tool that strengthens your impact but has no value until you apply it purposefully.
When you connect data to the essential points it supports, the transition should be explicit and sound like this:. If you have several significant points to make, consider demonstrating each with a new visualization.
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