il2 x data-presentation · guidelines for charts min. effort for reader ‣most important aspect...
TRANSCRIPT
Xavier DÉFAGO (professor)
Tokyo Institute of Technology School of Computing
July 2020
Data Presentation
most examples adapted from:
Raj Jain. The art of computer systems performance analysis.
Guidelines for ChartsMin. Effort for Reader ‣most important aspect ‣how much effort to understand?
Example ‣ legend box ‣direct labeling ‣axes labels
eg., “Daily CPU usage” ‣ include units
eg., “CPU [seconds]” 3
System Load
Response T
ime
A
B
C
System LoadResponse T
ime
B
A
C
Better
acceptable
Guidelines for ChartsAvoid Ambiguity ‣Show coordinate axis, scale divisions, origin ‣ Identify individual curves ‣Avoid potential source of misunderstanding
4System Load
Re
sp
on
se
Tim
e
A B
BAD
Common MistakesMany Variables on One Chart ‣ saves space, but harder to read. ‣=> message lost ‣better: three different graphs
5Number of users
Response T
ime [m
s]
Throughput
Response Time
Utilization
40
30
20
10
100
75
50
25
20
15
10
5
Utilization
[%]
Throughput
[s-1]
Too many variables
BAD
Common MistakesSymbols in Place of Text ‣ symbols => readers must search text ‣ saves writers time ‣ ... or not?!
readers skip => writer's time wasted
6λ
R µ = 1
µ = 3
µ = 2
Arrival Rate
Response
time 1 job/sec
3 jobs/sec
2 jobs/secBAD Better
Common MistakesLine Chart in Place of Column Chart ‣ joining points on line chart
=> intermediate values can be interpolated
7
糖分
[mg/個
]
0
75
150
225
300
柿 桃 梨 苺En
ergy
[kJ/
100g
]
0
100
200
300
柿 桃 梨 苺VERY BAD!! Better
Pictorial GamesNonzero Origin ‣emphasize or conceal the difference
8
600
625
650
675
700
Mine
Yours
0
1000
2000
3000
4000
5000
6000
Mine
Yours 0
250
500
750
1000
Mine
Yours
BADBAD Better
Pictorial GamesDouble-Whammy Graph ‣exaggerate impact
9
Throughput
Response time
Number of users
BAD
Pictorial GamesRandom Quantities w/o Confidence Intervals ‣hides variability of the information
10
Mine
Yours
Mine
Yours
BAD Better
Pictorial GamesInappropriate Cell Size in Histograms ‣possible loss of information
11
Freq
uenc
y
0
2
4
6
8
10
12
Response time [ms]
[0,2[ [2,4[ [4,6[ [6,8[ [8,10[ [10,12[
Freq
uenc
y
02468
101214161820
Response time [ms]
[0,6[ [6,12[
BADBetter
Pictorial GamesBroken Scales in Column Charts ‣exaggerate difference ‣ same as nonzero origin
12
Res
pons
e tim
e [m
s]
0
2
4
6
8
10
12
System
A B C D E F
8
9
10
11
12
Res
ponse
tim
e [m
s]
0
1
A B C D E F
System BADBetter
Misleading Pie Chart
13https://en.wikipedia.org/wiki/Misleading_graph
BAD Better
Improper Scaling
14https://en.wikipedia.org/wiki/Misleading_graph
BAD Better