最後我用不同的文件供圖熵的定義:
複雜網絡的信息理論:關於進化和建築約束
R.V.鞋底和S.巴爾韋德(2004)
和
網絡基於拓撲結構及其在隨機網絡計算熵
B.H。 Wang,W.X.王和T.周
計算每個的代碼如下。該代碼假定你有一個沒有自循環的無向圖,未加權圖。它將一個鄰接矩陣作爲輸入,並以位爲單位返回熵的數量。它在R中實現並使用sna package。
graphEntropy <- function(adj, type="SoleValverde") {
if (type == "SoleValverde") {
return(graphEntropySoleValverde(adj))
}
else {
return(graphEntropyWang(adj))
}
}
graphEntropySoleValverde <- function(adj) {
# Calculate Sole & Valverde, 2004 graph entropy
# Uses Equations 1 and 4
# First we need the denominator of q(k)
# To get it we need the probability of each degree
# First get the number of nodes with each degree
existingDegrees = degree(adj)/2
maxDegree = nrow(adj) - 1
allDegrees = 0:maxDegree
degreeDist = matrix(0, 3, length(allDegrees)+1) # Need an extra zero prob degree for later calculations
degreeDist[1,] = 0:(maxDegree+1)
for(aDegree in allDegrees) {
degreeDist[2,aDegree+1] = sum(existingDegrees == aDegree)
}
# Calculate probability of each degree
for(aDegree in allDegrees) {
degreeDist[3,aDegree+1] = degreeDist[2,aDegree+1]/sum(degreeDist[2,])
}
# Sum of all degrees mult by their probability
sumkPk = 0
for(aDegree in allDegrees) {
sumkPk = sumkPk + degreeDist[2,aDegree+1] * degreeDist[3,aDegree+1]
}
# Equivalent is sum(degreeDist[2,] * degreeDist[3,])
# Now we have all the pieces we need to calculate graph entropy
graphEntropy = 0
for(aDegree in 1:maxDegree) {
q.of.k = ((aDegree + 1)*degreeDist[3,aDegree+2])/sumkPk
# 0 log2(0) is defined as zero
if (q.of.k != 0) {
graphEntropy = graphEntropy + -1 * q.of.k * log2(q.of.k)
}
}
return(graphEntropy)
}
graphEntropyWang <- function(adj) {
# Calculate Wang, 2008 graph entropy
# Uses Equation 14
# bigN is simply the number of nodes
# littleP is the link probability. That is the same as graph density calculated by sna with gden().
bigN = nrow(adj)
littleP = gden(adj)
graphEntropy = 0
if (littleP != 1 && littleP != 0) {
graphEntropy = -1 * .5 * bigN * (bigN - 1) * (littleP * log2(littleP) + (1-littleP) * log2(1-littleP))
}
return(graphEntropy)
}
順便說一下,一旦我實現這些函數並計算真實圖的熵,我對這些措施感到失望。 Wang度量僅取決於圖的大小和密度,並且根本不考慮圖的結構。它主要是衡量密度。唯一度量反映了節點之間剩餘度數的多樣性。它比其他任何東西都更能反映出一種協調性。我仍然無法量化多麼複雜或不是一個圖。 –