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Added TimeSeries.wave_parameters

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master
per.andreas.brodtkorb 14 years ago
parent e2161e8696
commit 478846ee01
2 changed files with 226 additions and 178 deletions
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28
pywafo/src/wafo/doc/tutorial_scripts/chapter3.py
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@ -32,29 +32,19 @@ import wafo.kdetools as wk
clf()
print(Tc.mean())
print(Tc.max())
t = linspace(0.01,8,200);
ftc = wk.TKDE(Tc, L2=0, inc=128)
kopt = kdeoptset('L2',0);
tic
ftc1 = kde(Tc,kopt,t);
toc
pdfplot(ftc1), hold on
histgrm(Tc,[],[],1)
axis([0 8 0 0.5])
wafostamp([],'(ER)')
disp('Block = 2'), pause(pstate)
#!#!
tic
kopt.inc = 128;
ftc2 = kdebin(Tc,kopt);
toc
pdfplot(ftc2,'-.')
plot(t,ftc.eval_grid(t), t, ftc.eval_grid_fast(t),'-.')
wm.histgrm(Tc,scale=True)
title('Kernel Density Estimates')
hold off
disp('Block = 3'), pause(pstate)
axis([0, 8, 0, 0.5])
show()
#!#! Extreme waves - model check: the highest and steepest wave
clf
#! Extreme waves - model check: the highest and steepest wave
#!~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
clf()
method = 0;
rate = 8;
[S, H, Ac, At, Tcf, Tcb, z_ind, yn] = ...

360
pywafo/src/wafo/objects.py
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@ -1030,155 +1030,7 @@ class TimeSeries(WafoData):
# S.S = zeros(nf+1,m-1);
return spec
def wave_height_steepness(self, rate=1, method=1, g=None):
'''
Returns waveheights and steepnesses from data.
Parameters
----------
rate : scalar integer
interpolation rate. Interpolates with spline if greater than one.
method : scalar integer
0 max(Vcf, Vcb) and corresponding wave height Hd or Hu in H
1 crest front (rise) speed (Vcf) in S and wave height Hd in H. (default)
-1 crest back (fall) speed (Vcb) in S and waveheight Hu in H.
2 crest front steepness in S and the wave height Hd in H.
-2 crest back steepness in S and the wave height Hu in H.
3 total wave steepness in S and the wave height Hd in H
for zero-downcrossing waves.
-3 total wave steepness in S and the wave height Hu in H.
for zero-upcrossing waves.
Returns
-------
S, H = Steepness and the corresponding wave height according to method
The parameters are calculated as follows:
Crest front speed (velocity) = Vcf = Ac/Tcf
Crest back speed (velocity) = Vcb = Ac/Tcb
Crest front steepness = 2*pi*Ac./Td/Tcf/g
Crest back steepness = 2*pi*Ac./Tu/Tcb/g
Total wave steepness (zero-downcrossing wave) = 2*pi*Hd./Td.^2/g
Total wave steepness (zero-upcrossing wave) = 2*pi*Hu./Tu.^2/g
The definition of g, Ac,At, Tcf, etc. are given in gravity and
wafo.definitions.
Example
-------
>>> import wafo.data as wd
>>> import wafo.objects as wo
>>> x = wd.sea()
>>> ts = wo.mat2timeseries(x)
>>> for i in xrange(-3,4):
... S, H = ts.wave_height_steepness(method=i)
... print(S[:2],H[:2])
(array([ 0.01186982, 0.04852534]), array([ 0.69, 0.86]))
(array([ 0.02918363, 0.06385979]), array([ 0.69, 0.86]))
(array([ 0.27797411, 0.33585743]), array([ 0.69, 0.86]))
(array([ 0.60835634, 0.60930197]), array([ 0.42, 0.78]))
(array([ 0.60835634, 0.60930197]), array([ 0.42, 0.78]))
(array([ 0.10140867, 0.06141156]), array([ 0.42, 0.78]))
(array([ 0.01821413, 0.01236672]), array([ 0.42, 0.78]))
>>> import pylab as plt
>>> h = plt.plot(S,H,'.')
>>> h = plt.xlabel('S')
>>> h = plt.ylabel('Hd [m]')
See also
--------
wafo.definitions
'''
# Ac,At = crest and trough amplitude, respectively
# Tcf,
# Tcb = Crest front and crest (rear) back period, respectively
# z_ind = indices to the zero-crossings (d,u) of the defining
# trough to trough waves (tw). If M>1 then
# z_ind=[N1 z_ind1 N2 z_ind2 ...NM z_indM] where
# Ni = length(z_indi) and z_indi are the indices to
# the zero-crossings of xi, i=1,2...M.
#
# yn = interpolated signal
#
# xn = [ti x1 x2 ... xM], where
# ti = time and x1 x2 ... xM are M column vectors of
# sampled surface elevation.
#[S,H,z_ind2,AC1,AT1,TFRONT1,TREAR1]=deal([]); % Initialize to []
dT = self.sampling_period()
#[N M] = size(xx);
if g is None:
g = gravity() #% acceleration of gravity
if rate>1:
dT = dT/rate
t0, tn = self.args[0], self.args[-1]
n = len(self.args)
ti = linspace(t0, tn, int(rate*n))
xi = interp1d(self.args , self.data.ravel(), kind='cubic')(ti)
else:
ti, xi = self.args, self.data.ravel()
#for ix=2:M
tc_ind, z_ind = findtc(xi,v=0,kind='tw')
tc_a = xi[tc_ind]
tc_t = ti[tc_ind]
AC = tc_a[1::2] # crest amplitude
AT= -tc_a[0::2] # trough amplitude
if (0<= method and method <=2):
# time between zero-upcrossing and crest [s]
tu = ecross(ti, xi, z_ind[1:-1:2],v=0)
TFRONT = tc_t[1::2]-tu
TFRONT[(TFRONT==0)]=dT # avoiding division by zero
if (0 >= method and method>=-2):
# time between crest and zero-downcrossing [s]
td = ecross(ti,xi, z_ind[2::2],v=0)
TREAR = td-tc_t[1::2]
TREAR[(TREAR==0)]=dT; #% avoiding division by zero
if method==0:
# max(Vcf, Vcr) and the corresponding wave height Hd or Hu in H
HU = AC+AT[1:]
HD = AC+AT[:-1]
T = np.where(TFRONT<TREAR, TFRONT, TREAR)
S = AC/T
H = np.where(TFRONT<TREAR, HD, HU)
elif method==1: # extracting crest front velocity [m/s] and
# Zero-downcrossing wave height [m]
H = AC+AT[:-1] # Hd
S = AC/TFRONT
elif method== -1: # extracting crest rear velocity [m/s] and
# Zero-upcrossing wave height [m]
H = AC+AT[1:] #Hu
S = AC/TREAR
elif method== 2: #crest front steepness in S and the wave height Hd in H.
H = AC + AT[:-1] #Hd
T = diff(ecross(ti,xi, z_ind[::2],v=0))
S = 2*pi*AC/T/TFRONT/g
elif method== -2: # crest back steepness in S and the wave height Hu in H.
H = AC+AT[1:]
T = diff(ecross(ti,xi, z_ind[1::2],v=0))
S = 2*pi*AC/T/TREAR/g
elif method==3: # total steepness in S and the wave height Hd in H
# for zero-doewncrossing waves.
H = AC+AT[:-1]
T = diff(ecross(ti,xi , z_ind[::2],v=0))# Period zero-downcrossing waves
S = 2*pi*H/T**2/g
elif method== -3: # total steepness in S and the wave height Hu in H for
# zero-upcrossing waves.
H = AC+AT[1::]
T = diff(ecross(ti, xi, z_ind[1::2],v=0))# Period zero-upcrossing waves
S = 2*pi*H/T**2/g
return S, H
def _trdata_cdf(self, **options):
@ -1481,7 +1333,212 @@ class TimeSeries(WafoData):
mean = self.data.mean()
sigma = self.data.std()
return TurningPoints(self.data[ind], t, mean=mean, sigma=sigma)
def wave_parameters(self, rate=1):
'''
Returns several wave parameters from data.
Parameters
----------
rate : scalar integer
interpolation rate. Interpolates with spline if greater than one.
Returns
-------
parameters : dict
wave parameters such as
Ac, At : Crest and trough amplitude, respectively
Tcf, Tcb : Crest front and crest (rear) back period, respectively
Hu, Hd : zero-up-crossing and zero-downcrossing wave height, respectively.
Tu, Td : zero-up-crossing and zero-downcrossing wave period, respectively.
The definition of g, Ac,At, Tcf, etc. are given in gravity and
wafo.definitions.
Example
-------
>>> import wafo.data as wd
>>> import wafo.objects as wo
>>> x = wd.sea()
>>> ts = wo.mat2timeseries(x)
>>> wp = ts.wave_parameters()
>>> for name in ['Ac', 'At', 'Hu', 'Hd', 'Tu', 'Td', 'Tcf', 'Tcb']:
... print('%s' % name, wp[name][:2])
('Ac', array([ 0.25950546, 0.34950546]))
('At', array([ 0.16049454, 0.43049454]))
('Hu', array([ 0.69, 0.86]))
('Hd', array([ 0.42, 0.78]))
('Tu', array([ 6.10295202, 3.36978685]))
('Td', array([ 3.84377468, 6.35707656]))
('Tcf', array([ 0.42656819, 0.57361617]))
('Tcb', array([ 0.93355982, 1.04063638]))
>>> import pylab as plt
>>> h = plt.plot(wp['Td'],wp['Hd'],'.')
>>> h = plt.xlabel('Td [s]')
>>> h = plt.ylabel('Hd [m]')
See also
--------
wafo.definitions
'''
dT = self.sampling_period()
if rate > 1:
dT = dT / rate
t0, tn = self.args[0], self.args[-1]
n = len(self.args)
ti = linspace(t0, tn, int(rate * n))
xi = interp1d(self.args , self.data.ravel(), kind='cubic')(ti)
else:
ti, xi = self.args, self.data.ravel()
tc_ind, z_ind = findtc(xi, v=0, kind='tw')
tc_a = xi[tc_ind]
tc_t = ti[tc_ind]
Ac = tc_a[1::2] # crest amplitude
At = -tc_a[0::2] # trough amplitude
Hu = Ac + At[1:]
Hd = Ac + At[:-1]
tu = ecross(ti, xi, z_ind[1::2], v=0)
Tu = diff(tu)# Period zero-upcrossing waves
td = ecross(ti, xi , z_ind[::2], v=0)
Td = diff(td)# Period zero-downcrossing waves
Tcf = tc_t[1::2] - tu[:-1]
Tcf[(Tcf == 0)] = dT # avoiding division by zero
Tcb = td[1:] - tc_t[1::2]
Tcb[(Tcb == 0)] = dT; #% avoiding division by zero
return dict(Ac=Ac, At=At, Hu=Hu, Hd=Hd, Tu=Tu, Td=Td, Tcf=Tcf, Tcb=Tcb)
def wave_height_steepness(self, method=1, rate=1, g=None):
'''
Returns waveheights and steepnesses from data.
Parameters
----------
rate : scalar integer
interpolation rate. Interpolates with spline if greater than one.
method : scalar integer
0 max(Vcf, Vcb) and corresponding wave height Hd or Hu in H
1 crest front (rise) speed (Vcf) in S and wave height Hd in H. (default)
-1 crest back (fall) speed (Vcb) in S and waveheight Hu in H.
2 crest front steepness in S and the wave height Hd in H.
-2 crest back steepness in S and the wave height Hu in H.
3 total wave steepness in S and the wave height Hd in H
for zero-downcrossing waves.
-3 total wave steepness in S and the wave height Hu in H.
for zero-upcrossing waves.
Returns
-------
S, H = Steepness and the corresponding wave height according to method
The parameters are calculated as follows:
Crest front speed (velocity) = Vcf = Ac/Tcf
Crest back speed (velocity) = Vcb = Ac/Tcb
Crest front steepness = 2*pi*Ac./Td/Tcf/g
Crest back steepness = 2*pi*Ac./Tu/Tcb/g
Total wave steepness (zero-downcrossing wave) = 2*pi*Hd./Td.^2/g
Total wave steepness (zero-upcrossing wave) = 2*pi*Hu./Tu.^2/g
The definition of g, Ac,At, Tcf, etc. are given in gravity and
wafo.definitions.
Example
-------
>>> import wafo.data as wd
>>> import wafo.objects as wo
>>> x = wd.sea()
>>> ts = wo.mat2timeseries(x)
>>> for i in xrange(-3,4):
... S, H = ts.wave_height_steepness(method=i)
... print(S[:2],H[:2])
(array([ 0.01186982, 0.04852534]), array([ 0.69, 0.86]))
(array([ 0.02918363, 0.06385979]), array([ 0.69, 0.86]))
(array([ 0.27797411, 0.33585743]), array([ 0.69, 0.86]))
(array([ 0.60835634, 0.60930197]), array([ 0.42, 0.78]))
(array([ 0.60835634, 0.60930197]), array([ 0.42, 0.78]))
(array([ 0.10140867, 0.06141156]), array([ 0.42, 0.78]))
(array([ 0.01821413, 0.01236672]), array([ 0.42, 0.78]))
>>> import pylab as plt
>>> h = plt.plot(S,H,'.')
>>> h = plt.xlabel('S')
>>> h = plt.ylabel('Hd [m]')
See also
--------
wafo.definitions
'''
dT = self.sampling_period()
if g is None:
g = gravity() #% acceleration of gravity
if rate > 1:
dT = dT / rate
t0, tn = self.args[0], self.args[-1]
n = len(self.args)
ti = linspace(t0, tn, int(rate * n))
xi = interp1d(self.args , self.data.ravel(), kind='cubic')(ti)
else:
ti, xi = self.args, self.data.ravel()
tc_ind, z_ind = findtc(xi, v=0, kind='tw')
tc_a = xi[tc_ind]
tc_t = ti[tc_ind]
Ac = tc_a[1::2] # crest amplitude
At = -tc_a[0::2] # trough amplitude
if (0 <= method and method <= 2):
# time between zero-upcrossing and crest [s]
tu = ecross(ti, xi, z_ind[1:-1:2], v=0)
Tcf = tc_t[1::2] - tu
Tcf[(Tcf == 0)] = dT # avoiding division by zero
if (0 >= method and method >= -2):
# time between crest and zero-downcrossing [s]
td = ecross(ti, xi, z_ind[2::2], v=0)
Tcb = td - tc_t[1::2]
Tcb[(Tcb == 0)] = dT; #% avoiding division by zero
if method == 0:
# max(Vcf, Vcr) and the corresponding wave height Hd or Hu in H
Hu = Ac + At[1:]
Hd = Ac + At[:-1]
T = np.where(Tcf < Tcb, Tcf, Tcb)
S = Ac / T
H = np.where(Tcf < Tcb, Hd, Hu)
elif method == 1: # extracting crest front velocity [m/s] and
# Zero-downcrossing wave height [m]
H = Ac + At[:-1] # Hd
S = Ac / Tcf
elif method == -1: # extracting crest rear velocity [m/s] and
# Zero-upcrossing wave height [m]
H = Ac + At[1:] #Hu
S = Ac / Tcb
elif method == 2: #crest front steepness in S and the wave height Hd in H.
H = Ac + At[:-1] #Hd
Td = diff(ecross(ti, xi, z_ind[::2], v=0))
S = 2 * pi * Ac / Td / Tcf / g
elif method == -2: # crest back steepness in S and the wave height Hu in H.
H = Ac + At[1:]
Tu = diff(ecross(ti, xi, z_ind[1::2], v=0))
S = 2 * pi * Ac / Tu / Tcb / g
elif method == 3: # total steepness in S and the wave height Hd in H
# for zero-doewncrossing waves.
H = Ac + At[:-1]
Td = diff(ecross(ti, xi , z_ind[::2], v=0))# Period zero-downcrossing waves
S = 2 * pi * H / Td ** 2 / g
elif method == -3: # total steepness in S and the wave height Hu in H for
# zero-upcrossing waves.
H = Ac + At[1:]
Tu = diff(ecross(ti, xi, z_ind[1::2], v=0))# Period zero-upcrossing waves
S = 2 * pi * H / Tu ** 2 / g
return S, H
def wave_periods(self, vh=None, pdef='d2d', wdef=None, index=None, rate=1):
"""
Return sequence of wave periods/lengths from data.
@ -1540,10 +1597,11 @@ class TimeSeries(WafoData):
Example:
--------
Histogram of crest2crest waveperiods
>>> import wafo
>>> import wafo.data as wd
>>> import wafo.objects as wo
>>> import pylab as plb
>>> x = wafo.data.sea()
>>> ts = wafo.objects.mat2timeseries(x[0:400,:])
>>> x = wd.sea()
>>> ts = wo.mat2timeseries(x[0:400,:])
>>> T, ix = ts.wave_periods(vh=0.0,pdef='c2c')
>>> h = plb.hist(T)

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