def samp_start_path(z1,edge_pos,v):
# [edgeidx,z] = samp_start_path(z1,edge_pos,v)
# Samples a starting edge
# Inputs:
# z1- 2-element measurement list or array
# edge_pos- candidate edges (a list of arrays containing the positions of the edge nodes)
# v- measurement noise variance
# Outputs:
# edgeidx- index of sampled edge (integer)
# z- distance along edge (float)
nedge = len(edge_pos)
x1 = z1[0]
y1 = z1[1]
sqv = math.sqrt(v)
mui = numpy.zeros((nedge))
elli = numpy.zeros((nedge))
qrho = numpy.zeros((nedge))
# Compute weights for each edge
for i in range(nedge):
xi = edge_pos[i][0,0]
yi = edge_pos[i][1,0]
xe = edge_pos[i][0,1]
ye = edge_pos[i][1,1]
thi = math.atan2(ye-yi,xe-xi)
cth = math.cos(thi)
sth = math.sin(thi)
elli[i] = math.sqrt((xe-xi)**2+(ye-yi)**2)
mui[i] = (x1-xi)*cth+(y1-yi)*sth
P = mystats.normprob(mui[i],sqv,0,elli[i])
if abs(cth)>1e-10:
npdf = mystats.normpdf(y1-yi,(x1-xi)*sth/cth,sqv/abs(cth))/abs(cth)
else:
npdf = mystats.normpdf(x1-xi,(y1-yi)*cth/sth,sqv/abs(sth))/abs(sth)
qrho[i] = P*npdf/elli[i]
# Normalise weights
w = sum(qrho)
qrho = qrho/w
# Draw an edge
idx = mystats.drawmultinom(qrho)
# Draw the distance along the edge
z = mystats.tnorm(mui[idx],v,0,elli[idx])
return idx, z
def draw_location(t,path_pos,sk,segk,skm1,segkm1,tk,tkm1,vmean,vvar):
# [ssamp,segidx,logw] =
# draw_location(t,path_pos,sk,segk,skm1,segkm1,tk,tkm1,vmean,vvar):
# Sample a location between two points on the network
# Inputs:
# t- time at which sample is being drawn (float)
# path_pos- array of positions of path nodes (2 x q array of floats)
# (sk,segk)- position at time tk>t (float, integer)
# (skm1,segkm1)- position at time tkm1<t (float, integer)
# tk- next time (float)
# tkm1- previous time (float)
# (vmean,vvar)- - statistics of vehicle movement (floats)
# Outputs:
# ssamp- sample position on edge (float)
# segidx- index of sample along path (integer)
# logw- sample weight (float)
# Pre-allocate
nsegs = segk-segkm1+1 # This is the number of segments between the bracketing positions
Tbar = numpy.zeros((nsegs))
kap = numpy.zeros((nsegs))
ell = numpy.zeros((nsegs)) # total length of each segment
lb = numpy.zeros((nsegs))
ub = numpy.zeros((nsegs))
dist_cs = numpy.zeros((nsegs))
totell = 0
# For each segment, compute its length, mean duration and duration variance
if nsegs==1:
pos1 = path_pos[:,segkm1]
pos2 = path_pos[:,segkm1+1]
ell[0] = numpy.linalg.norm(pos1-pos2)
Tbar[0] = ell[0]/vmean
kap[0] = ell[0]*ell[0]*vvar/(vmean**4)
lb[0] = skm1
ub[0] = sk
totell = sk-skm1
dist_cs[0] = totell
else:
pos1 = path_pos[:,segkm1]
pos2 = path_pos[:,segkm1+1]
ell[0] = numpy.linalg.norm(pos1-pos2)
Tbar[0] = ell[0]/vmean
kap[0] = ell[0]*ell[0]*vvar/(vmean**4)
lb[0] = skm1
ub[0] = ell[0]
totell = ell[0]-skm1
dist_cs[0] = totell
for j in range(1,nsegs-1):
pos1 = path_pos[:,segkm1+j]
pos2 = path_pos[:,segkm1+j+1]
ell[j] = numpy.linalg.norm(pos1-pos2)
Tbar[j] = ell[j]/vmean
kap[j] = ell[j]*ell[j]*vvar/(vmean**4)
lb[j] = 0
ub[j] = ell[j]
totell = totell+ell[j]
dist_cs[j] = dist_cs[j-1]+ell[j]
j = nsegs-1
pos1 = path_pos[:,segk-1]
pos2 = path_pos[:,segk]
ell[j] = numpy.linalg.norm(pos1-pos2)
Tbar[j] = ell[j]/vmean
kap[j] = ell[j]*ell[j]*vvar/(vmean**4)
lb[j] = 0
ub[j] = sk
totell = totell+sk
dist_cs[j] = dist_cs[j-1]+sk
shat = numpy.zeros((nsegs))
lam = numpy.zeros((nsegs))
etilde = numpy.zeros((nsegs))
p2 = numpy.zeros((nsegs))
xi1 = numpy.zeros((nsegs))
xi2 = numpy.zeros((nsegs))
a1 = numpy.zeros((nsegs))
a2 = numpy.zeros((nsegs))
Ttilde1 = numpy.zeros((nsegs))
Ttilde2 = numpy.zeros((nsegs))
scfact = numpy.zeros(nsegs)
scfact[0] = (ell[0]-skm1)*(ell[0]-skm1)/(ell[0]*ell[0])
for b in range(1,nsegs-1):
scfact[b] = 1.
scfact[nsegs-1] = sk*sk/(ell[nsegs-1]*ell[nsegs-1])
# Compute the weights and sampling density for each segment
# First segment
a1[0] = -Tbar[0]/ell[0]
Ttilde1[0] = sk*Tbar[nsegs-1]/ell[nsegs-1]
for b in range(0,nsegs-1):
Ttilde1[0] += Tbar[b]
xi1[0] = kap[0]
for b in range(1,nsegs):
xi1[0] += scfact[b]*kap[b]
a2[0] = Tbar[0]/ell[0]
Ttilde2[0] = -skm1*Tbar[0]/ell[0]
xi2[0] = kap[0]
db = (a1[0]*a1[0]*xi2[0]+a2[0]*a2[0]*xi1[0])
shat[0] = (a2[0]*xi1[0]*(t-tkm1-Ttilde2[0])+a1[0]*xi2[0]*(tk-t-Ttilde1[0]))/db
lam[0] = xi1[0]*xi2[0]/db
p1 = mystats.normpdf(a2[0]*(tk-t-Ttilde1[0]),a1[0]*(t-tkm1-Ttilde2[0]),math.sqrt(db))
p2[0] = mystats.normprob(shat[0],math.sqrt(lam[0]),lb[0],ub[0])
etilde[0] = p1*p2[0]
for b in range(1,nsegs):
a1[b] = -Tbar[b]/ell[b]
a2[b] = Tbar[b]/ell[b]
Ttilde2[b] = Ttilde2[b-1]+Tbar[b-1]
Ttilde1[b] = Ttilde1[b-1]-Tbar[b-1]
xi2[b] = xi2[b-1]+(scfact[b-1]-1)*kap[b-1]+kap[b]
xi1[b] = xi1[b-1]-kap[b-1]+(1-scfact[b])*kap[b]
db = (a1[b]*a1[b]*xi2[b]+a2[b]*a2[b]*xi1[b])
shat[b] = (a2[b]*xi1[b]*(t-tkm1-Ttilde2[b])+a1[b]*xi2[b]*(tk-t-Ttilde1[b]))/db
lam[b] = xi1[b]*xi2[b]/db
p1 = mystats.normpdf(a2[b]*(tk-t-Ttilde1[b]),a1[b]*(t-tkm1-Ttilde2[b]),math.sqrt(db))
p2[b] = mystats.normprob(shat[b],math.sqrt(lam[b]),lb[b],ub[b])
etilde[b] = p1*p2[b]
# Normalise weights
e = etilde/numpy.sum(etilde)
# Draw a segment
segidx = mystats.drawmultinom(e)
# Draw a position in the segment
if segidx==0:
z = mystats.tnorm(shat[segidx],lam[segidx],skm1,ell[segidx])
elif segidx<(nsegs-1):
z = mystats.tnorm(shat[segidx],lam[segidx],0,ell[segidx])
else:
z = mystats.tnorm(shat[segidx],lam[segidx],0,sk)
# Sample weight (allow for approximate prior)
T1 = Ttilde1[segidx]+a1[segidx]*z
T2 = Ttilde2[segidx]+a2[segidx]*z
kap2 = 0
for b in range(0,segidx):
kap2 = kap2+(ub[b]-lb[b])*(ub[b]-lb[b])*kap[b]/(ell[b]*ell[b])
kap2 = kap2+(z-lb[segidx])*(z-lb[segidx])*kap[segidx]/(ell[segidx]*ell[segidx])
kap1 = (ub[segidx]-z)*(ub[segidx]-z)*kap[segidx]/(ell[segidx]*ell[segidx])
for b in range(segidx+1,nsegs):
kap1 = kap1+(ub[b]-lb[b])*(ub[b]-lb[b])*kap[b]/(ell[b]*ell[b])
logw = lognormpdf(tk-t,T1,kap1)+lognormpdf(t-tkm1,T2,kap2)
logw = logw-(lognormpdf(tk-t,T1,xi1[segidx])+lognormpdf(t-tkm1,T2,xi2[segidx]))
return z, segidx+segkm1, logw
def samp_path(z,t,cand_paths,turnpen,s0,v,vmean,vvar):
# [pathidx,segidx,z,logwt] = samp_path(z,t,cand_paths,turnpen,s0,v,vmean,vvar)
# Samples a path extension
# Inputs:
# z- 2-element measurement list or array of floats
# t- duration since last measurement
# cand_paths- candidate paths (a list of arrays containing the positions of each node on the path)
# turnpen- turn penalty along each path
# s0- starting position in final segment of each candidate path
# v- measurement noise variance
# (vmean,vvar)- statistics of vehicle movement
# Outputs:
# pathidx- index of sampled path (integer)
# segidx- segment along path in which vehicle lies (integer)
# z- distance along segment (float)
# logwt- log of sample weight (float)
npaths = len(cand_paths)
sqv = math.sqrt(v)
eps = numpy.spacing(1)
# Pre-allocate
x = z[0]
y = z[1]
gamma = numpy.zeros((npaths))
C1 = numpy.zeros((npaths))
qpath = numpy.zeros((npaths))
pathprior = numpy.zeros((npaths))
b = list(numpy.zeros((npaths)))
nu = list(numpy.zeros((npaths)))
zeta = list(numpy.zeros((npaths)))
ell = list(numpy.zeros((npaths)))
nsegs = [0 for i in range(npaths)]
lb = [0 for i in range(npaths)]
# Compute the weight of each path
for i in range(npaths):
sz_path = cand_paths[i].shape
nsegs[i] = sz_path[1]-1
if nsegs[i]==1:
lb[i] = s0[i]
else:
lb[i] = 0.
ell[i] = numpy.zeros(nsegs[i])
# Calculate prior mean and variance
# First segment (account for s0)
pos1 = cand_paths[i][:,0]
pos2 = cand_paths[i][:,1]
ell[i][0] = numpy.linalg.norm(pos1-pos2)
Tbarj = ell[i][0]/vmean
kapj = ell[i][0]*ell[i][0]*vvar/(vmean**4)
Ttilde = -s0[i]*Tbarj/ell[i][0]
kaptilde = 0.
c = (ell[i][0]-s0[i])/ell[i][0]
mean_term = Tbarj
var_term = c*c*kapj
for j in range(1,nsegs[i]):
pos1 = cand_paths[i][:,j]
pos2 = cand_paths[i][:,j+1]
ell[i][j] = numpy.linalg.norm(pos1-pos2)
Ttilde += mean_term
kaptilde += var_term
Tbarj = ell[i][j]/vmean
kapj = ell[i][j]*ell[i][j]*vvar/(vmean**4)
mean_term = Tbarj
var_term = kapj
# Compute location sampling density and path weight
xi = pos1[0]
yi = pos1[1]
xe = pos2[0]
ye = pos2[1]
thi = math.atan2(ye-yi,xe-xi)
cth = math.cos(thi)
sth = math.sin(thi)
mu = (x-xi)*cth+(y-yi)*sth
alph = ell[i][nsegs[i]-1]*(t-Ttilde)/Tbarj
lam = ell[i][nsegs[i]-1]*ell[i][nsegs[i]-1]*(kaptilde+kapj)/(Tbarj*Tbarj)
nu[i] = (v*alph+lam*mu)/(v+lam)
zeta[i] = lam*v/(v+lam)
if abs(cth)>1e-10:
npdf1 = mystats.normpdf(y-yi,(x-xi)*sth/cth,sqv/abs(cth))/abs(cth)
else:
npdf1 = mystats.normpdf(x-xi,(y-yi)*cth/sth,sqv/abs(sth))/abs(sth)
npdf2 = mystats.normpdf(mu,alph,math.sqrt(v+lam))
sqzeta = math.sqrt(zeta[i])
C2 = mystats.normprob(nu[i],sqzeta,lb[i],ell[i][nsegs[i]-1])
sqlam = math.sqrt(lam)
C1[i] = mystats.normprob(alph,sqlam,lb[i],ell[i][nsegs[i]-1])
pathprior[i] = 1/(numpy.sum(ell[i])+turnpen[i])
if npdf2>eps:
gamma[i] = npdf1*npdf2*C2/C1[i]
else:
gamma[i] = 0.
# Normalise path weights
pathprior = pathprior/numpy.sum(pathprior)
qpath = gamma*pathprior
wt = numpy.sum(qpath)
if wt<eps:
# Ignore zero weighted paths
pidx = 0
segidx = 0
ssamp = 0.
logwt = -1e10
isvalid = 0
return pidx, segidx, ssamp, logwt, isvalid
# If we get here we can sample a valid path
isvalid = 1
qpath = qpath/wt
# Sample a path
pidx = mystats.drawmultinom(qpath)
segidx = nsegs[pidx]-1
# Now sample a position
if nsegs[pidx]==1:
ssamp = mystats.tnorm(nu[pidx],zeta[pidx],s0[pidx],ell[pidx][nsegs[pidx]-1])
else:
ssamp = mystats.tnorm(nu[pidx],zeta[pidx],0,ell[pidx][nsegs[pidx]-1])
# Calculate sample weight
logwt = math.log(wt)+mystats.calc_samp_wt(t,ell[pidx],s0[pidx],ssamp,lb[pidx],C1[pidx],vmean,vvar)
return pidx, segidx, ssamp, logwt, isvalid
