10-1©2011 Raj JainCSE567MWashington University in St. LouisThe Art of The Art of Data PresentationData PresentationRaj Jain Washington University in Saint LouisSaint Louis, MO [email protected] slides are available on-line at:http://www.cse.wustl.edu/~jain/cse567-11/10-2©2011 Raj JainCSE567MWashington University in St. LouisOverviewOverview Types of Variables Guidelines for Preparing Good Charts Common Mistakes in Preparing Charts Pictorial Games Special Charts for Computer Performance Gantt Charts Kiviat Graphs Schumacher Charts Decision Maker’s Games10-3©2011 Raj JainCSE567MWashington University in St. LouisTypes of VariablesTypes of Variables Type of computer: Super computer, minicomputer, microcomputer Type of Workload: Scientific, engineering, educational Number of processors Response time of system10-4©2011 Raj JainCSE567MWashington University in St. LouisGuidelines for Preparing Good ChartsGuidelines for Preparing Good Charts Require minimum effort from the readerDirect labeling vs. legend box Maximize Information: Words in place of symbolsCleary label the axes10-5©2011 Raj JainCSE567MWashington University in St. LouisGuidelines (cont)Guidelines (cont) Minimize Ink: No grid lines, more details Use Commonly accepted practices: origin at (0,0)Independent variable (cause) along x axis, linear scales, increasing scales, equal divisions Avoid ambiguity: Show coordinate axes, scale divisions, origin. Identify individual curves and bars. See checklist in Box 10.110-6©2011 Raj JainCSE567MWashington University in St. LouisCommon Mistakes in Preparing ChartsCommon Mistakes in Preparing Charts Presenting too many alternatives on a single chartMax 5 to 7 messages Max 6 curves in a line charts, no more than 10 bars in a bar chart, max 8 components in a pie chart Presenting many y variables on a single chart10-7©2011 Raj JainCSE567MWashington University in St. LouisCommon Mistakes in Charts (Cont)Common Mistakes in Charts (Cont) Using symbols in place of text Placing extraneous information on the chart: grid lines, granularity of the grid lines Selecting scale ranges improperly: automatic selection by programs may not be appropriate10-8©2011 Raj JainCSE567MWashington University in St. LouisCommon Mistakes in Charts (Cont)Common Mistakes in Charts (Cont) Using a line chart in place of column chart: Line ContinuityCPU Type8000 8100 83008200MIPS10-9©2011 Raj JainCSE567MWashington University in St. LouisPictorial GamesPictorial Games Using non-zero origins to emphasize the differenceThree quarter high-rule height/width > 3/410-10©2011 Raj JainCSE567MWashington University in St. LouisPictorial Games (Cont)Pictorial Games (Cont) Using double-whammy graph for dramatizationUsing related metrics10-11©2011 Raj JainCSE567MWashington University in St. LouisPictorial Games (Cont)Pictorial Games (Cont) Plotting random quantities without showing confidence intervals10-12©2011 Raj JainCSE567MWashington University in St. LouisPictorial Games (Cont)Pictorial Games (Cont) Pictograms scaled by heightMinePerformance = 2YoursPerformance = 110-13©2011 Raj JainCSE567MWashington University in St. LouisPictorial Games (Cont)Pictorial Games (Cont) Using inappropriate cell size in histograms[0,2) [2,4) [4,6) [6,8)[8,10) [10,12) [0,6) [6,12)Response Time Response TimeFrequencyFrequency24681012024681012010-14©2011 Raj JainCSE567MWashington University in St. LouisPictorial Games (Cont)Pictorial Games (Cont) Using broken scales in column chartsASystemResp.Time246810120BCDEFASystemResp.Time0BCDEF910111210-15©2011 Raj JainCSE567MWashington University in St. LouisPerformance Analysis Rat HolesPerformance Analysis Rat HolesConfigurationWorkload Metrics Details10-16©2011 Raj JainCSE567MWashington University in St. LouisReasons for not Accepting an AnalysisReasons for not Accepting an Analysis This needs more analysis. You need a better understanding of the workload. It improves performance only for long IOs/packets/jobs/files, and most of the IOs/packets/jobs/files are short. It improves performance only for short IOs/packets/jobs/files, but who cares for the performance of short IOs/packets/jobs/files, its the long ones that impact the system. It needs too much memory/CPU/bandwidth and memory/CPU/bandwidth isn't free. It only saves us memory/CPU/bandwidth and memory/CPU/bandwidth is cheap.See Box 10.2 on page 162 of the book for a complete list10-17©2011 Raj JainCSE567MWashington University in St. LouisSummarySummary1. Qualitative/quantitative, ordered/unordered, discrete/continuous variables2. Good charts should require minimum effort from the reader and provide maximum information with minimum ink3. Use no more than 5-6 curves, select ranges properly, Three-quarter high rule4. Workload, metrics, configuration, and details can always be challenged. Should be carefully selected.10-18©2011 Raj JainCSE567MWashington University in St. LouisExercise 10.1Exercise 10.1What type of chart (line or bar) would you use to plot:a. CPU usage for 12 months of the yearb. CPU usage as a function of time in monthsc. Number of I/O's to three disk drives: A, B, and Cd. Number of I/O's as a function of number of disk drives in a system10-19©2011 Raj JainCSE567MWashington University in St. LouisExercise 10.2Exercise 10.2 List the problems with the following charts10-20©2011 Raj JainCSE567MWashington University in St. LouisHomework 10Homework 10 Read Chapter 10 Submit solutions to exercises 10.3 Approximate hand-drawn figures are
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