Charts and More

1. Charts and More Guilford County SciVis V105.04

2. Why use Graphs? • The purpose of any graph is to give a "physical" reality to the message contained in the data • Information presented in chart form is clearer and more memorable than text

3. Rules for Charts • Remember "One Slide, One Message, One Chart!" • Each chart must have a single, well-defined message to present to the audience • Always make sure that the title of any chart clearly describes the message of the chart.

4. Basic Chart and Graph Layout Each graphic item in a chart represents two pieces of information: • The name of a measurable item (called a category) which is identified on the chart by a label, and • A quantity associated with the item (called a data point) which is plotted on the chart as a value.

5. There are two basic types of plotting areas: rectangular and circular Basic Chart and Graph Layout cont…

6. Rectangular Plotting Areas The basic elements of a rectangular plotting area include: • The Chart Frame; which defines the boundaries of the plotting area. • The Scale; which acts as a ruler for the audience to measure the relative size or position of the plotted values. • The Labels; which name the items being plotted. • The Grid or Tick marks; which act as guidelines and markers for the scale

7. The basic chart frame consists of a box which defines the area in which your data will be plotted. Rectangular Chart Frames

8. Full Frame Half Frame Baseline Only No Frame Frame Options

9. Rectangular Chart Scales • The values in a chart are plotted against a grid or scale which allows you to measure the relative size of the items . • The basic grid for most charts consists of an X axis and a Y axis. The X axis extends from left to right, the Y axis extends from bottom to top.

10. Chart Scale Rules 1. Keep Scale Increments Evenly SpacedThe spacing and values of your scale should be evenly distributed 2. Keep Scale Figures Readable The text size of your scale figures should be at least half the size of the average body text used in your slides

11. Chart Scale Rules 3. Limit The Number of Scale Steps Use no more than ten steps in any scale on a slide. A scale should also contain a minimum of four steps to be a useful ruler for the audience

12. Grids & Tickmarks • A grid line is one which extends across the entire chart frame. • A tick mark is a shorter line which indicates a scale division. • Grids and tick marks can also be combined.

13. Grids & Tick marks

14. Axis Titles • Used to label values on an axis • Used for very large numbers • Keep axis titles short and to the point

15. Axis Labels • Axis labels are placed under each graphic on the X-axis to identify the category • Should be spaced evenly along the axis • Two ways of setting up axis labels: object-aligned and grid-aligned. • 1. Object-aligned labels used with a graphic object such as a bar -does not need any sort of grid or tick mark. • 2. Grid-aligned labels used with line and area charts when it is necessary to line up labels at bottom of the chart frame with data points some distance away.

16. Axis Labels

17. Data values are text used to show the actual value of a chart item, such as column values or pie percentages. Data values should be placed either inside or directly adjacent to the chart graphic Keep data values short $30.6 M", not "$30,609,784.23". Data Values

18. A descriptive text placed in a chart which is not data or part of the axes Used to identify lines when there is more than one in a line chart Keep as simple as possible Callouts

19. A visual key used to identify chart segments when labels and callouts are inadequate Never use a legend where you can use labels or callouts Legends

20. Independent Variable The predetermined number, called the independent variable, is given a horizontal (x) position Use the horizontal axis for time Dependent Variable The number or value you are measuring is called the dependent variable, is given a vertical (y) position Independent and Dependent Variable In a scientific experiment, the experimenter chooses values for the independent variable, runs the experiment, and measures the dependent variable.

21. Examples of Variables Go to these web sites and read the examples. http://www.kmsi.org/curriculum/kmsi/sharedconcepts/data/represent/graph/variables/independent.htm http://www.kmsi.org/curriculum/kmsi/sharedconcepts/data/represent/graph/variables/Independent%20&%20Dependent.ppt

22. STEPS IN GRAPHING • STEP 1: Select the graph paper. • STEP 2: Identify the dependent and the independent variables. • STEP 3: Scale the axes. • STEP 4: Assign values to the origin of the graph. • STEP 5: Number each major division along each axis. • STEP 6: Complete labeling of both axes. • STEP 7: Title the graph. • STEP 8: Plot the data points. • STEP 9: Draw a smooth curve.

23. Selecting the Correct Chart Type Line Graphs • Most common and useful chart for presenting information • Best when showing trends, displaying increases and decreases, and showing relationships • Treated as a column chart, this data is overbearing. As a line chart, it gives a clean, accurate picture of growth.

24. X and Y scale Half or full frame Staff grid can be used Plot line should be thick 3-4 times thicker than grid lines Choose bright, contrasting colors for lines Identify each line with a label No more that 4 lines on a chart Choose your grid based on the amount of accuracy required Don’t include data labels Line Graph Layout

25. Line graph Variations Step Line Charts • Plot abrupt change rather than gradual.Their purpose is to show "plateaus" of values related to time

26. Adding depth to a line chart creates a "ribbon" which is usually confusing and adds nothing to your chart Adding Depth to Line Charts

27. Selecting the Correct Chart Type Bar or Column Graphs: • Used to display the relative size or volume of tangible, physical things. • For example, use them to compare weights, dollar values, and object quantities

28. Examples of column Charts

29. Columns should be evenly spaced • The space between columns should be no less than 25% and no more than 100% of the column width

30. Stacked Column Grouped Column Bar and Column Variations

31. Grouped Columns Groups can be arranged with columns touching, or slightly overlapping. Overlap not more than one third of total width. The tallest column should be in the back, with shorter columns ranked in front of it

32. Histogram A special column where you use a variable scale for both axes • Width of a column also carries information • Y-scale is the same as any other column chart • X-axis acts as another scale in which the width represents a span of time or other variable • columns in a histogram should always touch

33. Adding Depth 2 methods 1. Perspective depth-column surface is extruded backwards Problems: Hard to get right Audience views graph from different angles True perspective does not work well with Y-axis scale, since the depth distorts the columns' relationship with the scale. Column Chart Enhancements

34. Adding Depth 2 methods 1. Oblique depth -the surface of the column is extruded. Problems: Easy to misrepresent data Column Chart Enhancements

35. Bar Charts • Rotated version of the column chart • Used to compare the relative size of items • Possible to have longer labels for bars • Good for showing the rankings of items • Ascending or descending order not alpha

36. Bar Chart Layout • Labels on the Y axis identify each bar. • Scale on X to measure the length of the bar • scale at the bottom of the plotting area • bars should be evenly spaced • bars should use most of the height of the plotting area • space between bars should be no less than 25% and no more than 100% of the bar thickness • longest bar should also use as much of the full width of the plotting area as possible

37. Adding Depth to Bar Charts • Same as for the column • There is a tradeoff between dramatic graphics and accuracy

38. Scatter Charts • tool for plotting "points" on 2 scales, where there is no direct trend between the data. • Each dot or mark on the chart represents 2 data values along the X and Y axes. • Both axes are usually continuous scales

39. Scatter graph layout • layout is similar to line charts • attach a label to each dot • limit plot points to less than ten • use color to differentiate your categories

40. adds a third dimension to the scatter chart the dot’s size also acts as a data value data should be reflected in the AREA of the circle, not its radius or diameter Bubble Chart

41. substitutes appropriate graphic icons for the traditional graphics of bar and column charts guidelines Keep symbols simple. Symbols should be appropriate to the topic of the chart. Data value changes should be represented by more or fewer symbols, not by the size of the symbols. Pictographs are often visually inaccurate. Include data values for precision. Pictograph charts

42. Pie Charts • shows the relationship between the parts of a whole

43. Pie Chart Layout • scale of a pie chart is always 0 to 100 percent • All data needs to be converted into percentages • Try to limit your pie charts to no more than six pie segments to maintain clarity • avoid using a legend- Use labels inside • Since people read clockwise, the most important pie segment should begin at the 12 o'clock point of a flat pie chart • highlight segments of a pie chart by pulling a segment out of the complete circle

44. The "exploded" segment can also be highlighted with a brighter color for further emphasis. Pie Chart

45. Adding Depth to Pie Charts • Three dimensional pie charts are very dramatic. • The most common form is simply a thick disk tilted back, showing the front edge of the pie.

46. Problems with Depth in Pie Charts • tend to visually distort the data • Pie segments • at the top of the • chart are diminished • Pie segments at the bottom are over emphasized • You can use this effect to your advantage by placing a segment you want to emphasize at the bottom

47. Proportional Pie Charts 100% Stacked Column Chart Variations on Pie Charts

48. Flow/Process Charts • Picture description of a procedure followed to solve a problem • shows relationships between people and processes rather than numbers • Common use -computer programs • To perform the process start at the top and move from box to box.

49. input output

50. How to Make a Flowchart • Determine the beginning and end of a process. • Brainstorm all major inputs, outputs, and processes • Use “post it” notes to sequence events and arrange them for all to see • Walk through. Check for smoothness. Make changes. Apply.