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Using Graphics to Think Preparing the graphics first helps you accomplish two tasks: –get started –provide a visual framework for your written or spoken communication.

Which visual representation will bring out the meaning of the data best? Choice of visual representation can reveal new relationships among data. Representing the data differently can lead to new findings.

In 1854, Dr. John Snow made a map of deaths from the cholera epidemic in London. Tufte, Visual Explanations, 1997 Previously, data on deaths had been displayed chronologically. Example: representing deaths as a map

Figure 2. Reported Illness and Death in London in 1854 Numbers of People

Brewery Work House

Choice of data display can be life- saving. Snow took data normally displayed chronologically and graphed them spatially. Spatial display convinced the authorities to shut down the Broad St. pump. –From that moment, cholera was seriously understood to be linked to pathogens in water.

You want to establish useful relationships among the data.  Map makes quantitative comparisons visible and locates them spatially.  Map is good for showing cause and effect.  Time series chart not as effective for showing cause and effect (except in controlled experiments). “... the way in which we present the data determines what can be seen in the data.” Valiela, Doing Science, p. 183

So, you may have two questions... When should I display data? –What can the graphic do that words alone cannot? What makes a good and useful graphic?

When to use a graphic: To show complex data in a simplified form To show a lot of data in one place To emphasize relationship better than can words alone To help the reader remember To allow parallel processing of info.

What makes a graphic useful? Expert on principles of good information design: Edward Tufte. –The Visual Display of Quantitative Information, 1983 –Envisioning Information, 1990 –Visual Explanations, 1997

Create a simple design for complex information.

Beware the default parameters in Excel!

Figure 1. Deflection of Concrete Beams under Various Loads Much Better!

Two major types of graphics: two labels –Graphs –Charts –Drawings and Schematics –Photographs 45

Visual data cannot be understood without proper labeling. Label each graphic clearly with a figure or table number and a title. –Place the figure number and title beneath a figure (anything not a table). –Place the table number and title above a table.

100 cm (Air Outlet) 0 cm 50 cm 75 cm Bioreactor Packing Air Sampling Points 25 cm Column Position (X) Contaminated Air Inlet Figure 5.2. Schematic of the experimental bioreactor

Table 2: Example of Table with Modified Parameters

More Labeling Guidelines Label both axes. These labels are NOT optional. Provide common abbreviations or symbols for units. Explain less common ones.

Create a title that draws attention to significant aspects of the graphic. Figure 2. Material Cost per Linear Foot for each Eight-Foot High Wall Design Cost computed using RS Means 2002 Building Construction Cost Data. 0 Wall Design SSWw/RC SSWw/SDBStSW StSWw/SDBDSW DSWw/SDB

Integrate graphics with your text. In the body of the document, make sure you do the following: –Describe everything graphed. For tables, explain column headings, at least. –Draw attention to important features of data. Try to include these features in the title too. –Describe conclusions drawn from the data. What’s significant about those data or findings? Place graphic close to its discussion. Explanation and significance described fully in the text.

Coefficient of Thermal Expansion/Shrinkage A low coefficient of thermal expansion indicates that the material will have minimal change in length given temperature fluctuations. Thermal coefficients for the patching materials are summarized in Table 4; as can be seen, FRP overlay has the lowest. Table 4. Coefficients of Thermal Expansion/Shrinkage for Patching Materials Patching Material Thermal Coefficient (x106/°C) (Target Property Values)(14) High Density Low Slump Concrete 7-20 Fiberglass jacketsNot Available Latex Modified Concrete13-23 Epoxy Resin-Concrete Composite FRP Overlay5.5

Material Cost According to our calculations, the DSWw/SDB has the highest material cost of $16.38 per linear foot.... All material costs are for an eight-foot high wall. The material cost calculations we developed are shown in Appendix A, and the material costs are summarized in Figure 2. Figure 2. Material Cost per Linear Foot for each Eight-Foot High Wall Design Cost computed using RS Means 2002 Building Construction Cost Data. 0 Wall Design SSWw/RC SSWw/SDBStSW StSWw/SDBDSW DSWw/SDB Provide important details in title and in text.

 Cite the source of every “borrowed” graphic, under the title. Crop as needed.

Figure 2. United States Facilities with No. 2 Emissions Source: Environmental Protection Agency, 2000,

Correct Labeling: Cite source of data Figure 3. Relationship between density and temperature of air at standard atmospheric pressure. Source of data: Crowe, et al. Engineering Fluid Mechanics, 2001

Talking to experts: Interviews Gather some information ahead of time. Prepare effective questions –focused –few yes/no –one at a time Don’t interrupt Allow time for response Convey interest –tone of voice & body language Write thank-you letter