def corr_v(M, t, indices, avg=1, axes=['Ux', 'Ux'], p=1, average=False):
C = []
C_norm = []
X, Y = chose_axe(M, t, axes)
if average:
Xmoy, Xstd = statP.average(X)
Ymoy, Ystd = statP.average(Y)
else:
Xmoy = 0
Xstd = 0
Ymoy = 0
Ystd = 0
for i, j in indices.keys():
# print(indices[i,j])
k, l = indices[i, j]
Sp = (X[i, j] - Xmoy)**p * (
Y[k, l] -
Ymoy)**p #remove the average in space ? -> remove by default
C.append(Sp) # for k,l in indices[(i,j)]])
Sp_norm = (X[i, j] - Xmoy)**(2 * p)
C_norm.append(Sp_norm)
# substract the mean flow ? it shouldn't change the result so much, as there is no strong mean flow
#-> to be checked
# how to compute the mean flow : at which scale ? box size ? local average ?
# Cmoy,Cstd=average(C)
Cf = statP.average(C)[0] / statP.average(C_norm)[0]
return Cf
def corr_d(M,
frame,
indices=None,
dlist=None,
axes=['Ux', 'Ux'],
p=1,
average=False):
"""
Compute the correlation function in time at a given instant
INPUT
-----
M : Mdata object
frame : int
frame index
indices : dict of 2 elements tuple (for both keys and values)
pairs of coordinates that defines the distance of computation.
Default value is None : compute the pair of indices directly
dlist : list
distances between points. defaut is None (goes with indices)
axes : 2 element string list
field names to be used
p : int
order of the correlation function
OUTPUT
-----
dlist : list of distances beetween points
C : correlation function (un-normalized)
"""
if indices is None:
dlist, indices = get_indices(M)
# else:
# print('dlist ?')
C = []
X, Y = access.chose_axe(M, frame, axes)
if average:
Xmoy, Xstd = statP.average(X)
Ymoy, Ystd = statP.average(Y)
else:
Xmoy = 0
Xstd = 0
Ymoy = 0
Ystd = 0
C = [[] for i in indices]
for m, ind in enumerate(indices):
for i, j in ind.keys():
k, l = ind[i, j]
Sp = (X[i, j] - Xmoy)**p * (
Y[k, l] -
Ymoy)**p #remove the average in space ? -> remove by default
C[m].append(Sp) # for k,l in indices[(i,j)]])
C[m], std = statP.average(C[m])
return dlist, C
def structure_function(M, t, indices, axes=['E', 'E'], p=2):
"""
Compute structure functions from a Mdata set
INPUT
-----
M : Mdata object
t : int
time index
indices : list of tuple
list of pair of indices, used as the sample of Mdata to compute two points quantities
axe : string.
Possible values are : 'E', 'xx', 'yy', 'xy'
to be implemented : 'l' : longitudinal, 't' : transverse
OUTPUT
-----
C : list of float
list of evaluated structure functions on the positions specified by the list indices
"""
X, Y = chose_axe(M, t, axes)
C = []
for i, j in indices.keys():
for k, l in zip(indices[(i, j)][0], indices[(i, j)][1]):
C.append(X[i, j]**p - Y[k, l]**p) # for k,l in indices[(i,j)]])
# print(len(C))
Cmoy, Cstd = statP.average(C)
return C
def corr_v_tn(M, t, indices, avg=1, p=1):
"""
Compute the correlation coefficient at time t for a collection of pair indices
INPUT
M : Mdata object
t : time indice
indices : dictionnary containing pair of indices
"""
C = []
x = M.x
y = M.y
Ux = M.Ux[..., t]
Uy = M.Uy[..., t]
Xmoy, Xstd = statP.average(Ux)
Ymoy, Ystd = statP.average(Uy)
for i, j in indices.keys():
k, l = indices[i, j]
#tangent vector
u = (x[k, l] - x[i, j], y[k, l] - y[i, j])
theta, r = Smath.cart2pol(u)
Sp = (X[i, j] - Xmoy)**p * (Y[k, l] -
Ymoy)**p #remove the average in space ?
# for k,l in zip(indices[(i,j)][0],indices[(i,j)][1]):
C.append(Sp) # for k,l in indices[(i,j)]])
# substract the mean flow ? it shouldn't change the result so much
# but it does change !
# at which scale ? box size ? local average ?
#
# Cmoy,Cstd=average(C)
return statP.average(C)
def corr_d_stat(M, N, indices=None, axes=['Ux', 'Ux'], p=1, average=False):
"""
Compute the correlation function from an ensemble N of time
"""
#select N times to compute the
if indices is None:
dlist, indices = get_indices(M)
nx, ny, nt = M.shape()
frames = range(0, nt, nt / N)
Ctot = [[] for i in frames]
for i, frame in enumerate(frames):
d, Ctot[i] = corr_d(M,
frame,
indices=indices,
dlist=dlist,
axes=axes,
p=p,
average=average)
Ctot = np.asarray(Ctot)
Ctot, Cstd = statP.average(Ctot, axis=0)
return dlist, Ctot
def corr_v_d(Mlist,
t,
axes=['Ux', 'Ux'],
N=100,
Dt=1,
p=1,
display=False,
save=False,
label='^',
fignum=1):
"""
compute the correlation function in space at a given time. Average over space (ie along d-1 dimensions of Mlist[axes[0]]),and eventually over time
INPUT
------
M : Mdata object
must have attributes : t, fields ('Ux','Uy', ...)
must have method shape()
t : int
time index
axes : 2 elements string list
attributes of M to be used for the correlation function
N : int
Number of frames before and after time t.
p : int. default value is 1
power of the fields C_p(Dt) = U1**p * U2**p / <U1**2p >
display : bool. default value is false
"""
# Ct=[]
#how to average ?? -> need a mean on several realization ? or just substract the average value (in space) ?
M = Mlist[0]
tlist = M.t
# print("Compute mean values")
tmin = max(0, t - N)
tmax = min(len(tlist) - 1, t + N)
#print(tmin)
#print(tmax)
t_c = np.asarray(M.t)[np.arange(tmin, tmax)] #-M.t[t]
# print(np.mean(np.diff(t_c)))
#max number of time step
# print("Compute mean values 2")
#Compute the average flow
Xm = []
Ym = []
for M in Mlist:
Xref, Yref = chose_axe(M, t, axes)
Xm.append(Xref)
Ym.append(Yref)
Xm = np.asarray(Xm)
Ym = np.asarray(Ym)
# print(Xm.shape)
Xmoy_ref, Xstd_ref = statP.average(Xref, axis=())
#idea : compute the flow average over several realizations (ensemble avg)
Ct = []
for tc in range(tmin, tmax):
Sp = []
Xt_moy = []
XDt_moy = []
for M in Mlist:
Xref, Yref = chose_axe(M, t, axes)
Xt_m, Xstd_ref = statP.average(Xref)
Xt_moy.append(Xt_m)
X, Y = chose_axe(M, tc, axes)
XDt_m, Xstd = statP.average(X)
XDt_moy.append(XDt_m)
Xt_ref = statP.average(Xt_moy)
XDt_ref = statP.average(XDt_moy)
for M in Mlist:
Xref, Yref = chose_axe(M, t, axes)
# Xmoy_ref,Xstd_ref=statP.average(Xref)
X, Y = chose_axe(M, tc, axes)
# Xmoy,Xstd=statP.average(X)
Sp.append((X - XDt_ref)**p * (Xref - XDt_ref)**p)
# print(np.shape(Sp))
Ct.append(statP.average(Sp)[0])
# print(Ct)
C0 = Ct[t - tmin]
C_norm = np.asarray(Ct) / C0
indices = np.argsort(t_c)
t_c = t_c[indices] - M.t[t]
C_norm = C_norm[indices]
#plot distribution of Sp values ?
figs = {}
if display or save:
field = axes[0]
title = str(axes[0]) + ', ' + str(axes[1])
graphes.graph(t_c, C_norm, fignum=fignum, label=label)
figs.update(graphes.legende('$t (s)$', '$C$', title))
if save:
name = 'fx_' + str(int(np.floor(M.fx * 1000))) + 'm_t_' + str(
int(np.floor(M.t[t] * 1000))) + 'm_'
graphes.save_figs(figs,
prefix='./Stat_avg/Time_correlation/Serie/' +
field + '/' + name,
dpi=300,
display=True,
frmt='png')
return t_c, C_norm