On the Analysis of Optical Mapping Data - University of Wisconsin ...

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0.20
0.15
0.10
0.05
0.00
0.700 − 0.005
10 20 30 40 50 60
0.750 − 0.005 0.800 − 0.005
0.700 − 0.003 0.750 − 0.003
0.800 − 0.003
0.20
P(X = x)
0.15
0.10
0.05
0.00
0.20
0.15
0.10
0.05
0.00
0.700 − 0.001 0.750 − 0.001
0.800 − 0.001
10 20 30 40 50 60
x
10 20 30 40 50 60
Figure 2.8 A hanging rootogram comparing the observed distribution of the number of
fragments in GM07535 optical maps to various simulated map sets. The rootogram, an
innovation due to John Tukey, is intended to compare the distribution of a discrete random
variable to a reference distribution. Here, the continuous reference curve represents the
relative frequencies of number of fragments observed in the GM07535 data and is the same
in each panel. The vertical lines represent corresponding frequencies in simulated data, but
they ‘hang’ from the reference rather than starting from the origin. Systematic departures
from the reference are indicated by patterns of the lower endpoints relative to the origin.
Also, the vertical axis plots the square root of the proportions (hence the name rootogram)
to emphasize smaller probabilities.