From: Stringent response of Escherichia coli: revisiting the bibliome using literature mining
Frequency
fre q t i = D t i D = # d o c s t i # d o c s
(Eq. 1)
Mean
mea n t i = μ t i = # a n n o t s t i # d o c s t i
(Eq. 2)
Standard deviation
st d t i = σ t i = 1 / # d o c s t i ∑ j = 1 # d o c s t i ( # a n n o t s t i , d o c j - μ t i ) 2
(Eq. 3)
Variance-to-mean
VM R t i = σ t i 2 μ t i
(Eq. 4)
Co-annotation
fre q t i , t j = D t i ∩ t j D t i = # d o c s t i ∩ t j # d o c s t i
(Eq. 5)