ftide: Fit Tidal Data
In TideHarmonics: Harmonic Analysis of Tides
Description
Usage
Arguments
Details
Value
See Also
Examples
Description
Fit tidal data using any of over 400 harmonic constituents.
Daily nodal corrections and time-varying mean sea-levels
can be used.
Usage
1
2
Arguments
x
A numeric vector or time series object giving the
sea-levels. Missing values are allowed.
dto
A date/time vector of the same length as x,
which should be a POSIXct object or something which can be
converted to a POSIXct object. If no time zone is given then
UTC is assumed. No missing values are allowed.
hcn
A vector of constituent names. Some in-built vectors
of names can be used: hc4, hc7, hc37, hc60 and hc114. If not
specified, the vector hc60 is used by default.
astlon
The longitude formula to be used. The default
"task" is the formulas use in the TASK-2000 software. The
alternative "cartwright" uses Cartwright(1982).
nodal
Should nodal corrections be be used?
smsl
If TRUE, then a smooth curve is fitted to
the mean sea-level based on the loess function. This is
designed to account for smooth changes at periods longer
than the lowest speed harmonic, which by default is the
solar annual term Sa.
span, degree
Arguments passed to the loess function.
...
Passed to the linear model function lm.
Details
The function first removes the mean sea-level from the data
(which by default is a single number) and the fits a linear
model without intercept to sine and cosine terms defined by
the specified harmonics. This (by default) includes nodal
corrections. The sine and cosine coefficients can then be used
to derive the amplitude and phases. See the package vignette
for details.
Different names are used by various organizations for identical
constituents. This package is designed to be robust, so that
any common name can be used. In the output, the name will get
converted to the set of names that we employ.
For constituents based on underlying components, we use our own
(logical) naming scheme rather than the (totally confusing)
historical scheme. See harmonics and the package
vignette for details. Either scheme should work for the input
vector hcn.
The UTC time zone is assumed by default. Even if a different
time zone is used, the phase lags will be calculated in UTC.
The utc argument of coef.tide can be used to
derive phase lags for different time zones.
An error will be produced if two specified harmonic
components have virtually identical speeds (specifically, if the
first five Doodson numbers are the same), even if the nodal
corrections are different. This is to avoid numerical problems
in the linear model fit, because these components will be
difficult (or impossible) to identify separately.
The slowest harmonics in the default hc60 vector is the annual
solar term Sa. If you do not have at least one year of data you
should not include Sa. The fastest harmonics in hc60 have periods
of just over 4 hours. If your frequency of observation is more
than 2 hours you should not include the faster constituents.
Value
A list object of class c('tide','lm'). This is exactly the
save as a standard lm object but with the following
additional components
fval
The form factor, which in terms of amplitudes is
calculated as (K1+O1)/(M2+S2). This component and the two
components given below are only available if all four of these
harmonics are included in the fit.
features1
A vector of fitted features that are relevant
for semi-diurnal sites. MLWS = Mean Low Water Springs. MLWN =
Mean Low Water Neaps. MSL = Mean Sea-Level. MHWN = Mean High
Water Neaps. MHWS = Mean High Water Springs.
features2
A vector of fitted features that are relevant
for diurnal or mixed semi-diurnal sites. MLLW = Mean Lower Low
Water. MHLW = Mean Higher Low Water. MSL = Mean Sea-Level. MLHW =
Mean Lower High Water. MHHW = Mean Higher High Water.
cfmat
A matrix of sine and cosine coefficients, in the
same order as the hcn vector.
cfmat
A matrix of amplitudes, phase lags, sine and cosine
coefficients, ordered by decreasing amplitude.
origin
The POSIXct value used as the origin, which is in
the centre of the dto vector.
vn0
A named vector containing reference signals (equilibrium
phases) in degrees for each harmonic constituent.
msl
The mean sea level, either a vector (if smsl is
TRUE) or a single number (if smsl is FALSE).
lobj
The fitted loess object if smsl is TRUE.
nodal
The nodal argument.
astlon
The astlon argument.
See Also
harmonics, hc114, plot.tide, predict.tide
Examples
1
2
3
4
Example output
Call:
lm(formula = x ~ -1 + ., data = xmat, na.action = na.exclude)
Form Factor: 2.991049
Features (Diurnal or Mixed):
MLLW MHLW MSL MLHW MHHW
0.4676174 0.5723951 0.8113304 1.0502657 1.1550435
Harmonics:
amplitude phase sine cosine
K1 1.733e-01 1.973e+02 -5.147e-02 -1.655e-01
O1 1.181e-01 2.144e+02 -6.673e-02 -9.738e-02
Sa 9.930e-02 4.774e+01 7.350e-02 6.678e-02
P1 5.462e-02 1.903e+02 -9.720e-03 -5.375e-02
M2 5.239e-02 1.096e+02 4.936e-02 -1.757e-02
S2 4.501e-02 8.800e+01 4.498e-02 1.573e-03
Q1 2.956e-02 2.191e+02 -1.865e-02 -2.293e-02
Mf 2.300e-02 3.561e+02 -1.567e-03 2.294e-02
S1 2.223e-02 3.306e+02 -1.092e-02 1.936e-02
Ssa 1.998e-02 1.629e+02 5.862e-03 -1.910e-02
N2 1.582e-02 1.733e+02 1.833e-03 -1.571e-02
K2 1.398e-02 8.040e+01 1.378e-02 2.331e-03
Mm 1.073e-02 4.210e+01 7.196e-03 7.963e-03
J1 1.037e-02 2.058e+02 -4.523e-03 -9.337e-03
mu2 7.204e-03 1.682e+02 1.476e-03 -7.051e-03
MSf 6.632e-03 1.454e+02 3.766e-03 -5.458e-03
2Q1 5.091e-03 2.221e+02 -3.414e-03 -3.777e-03
rho1 4.946e-03 2.101e+02 -2.481e-03 -4.279e-03
M4 4.730e-03 2.686e+02 -4.729e-03 -1.124e-04
M1 4.728e-03 2.577e+02 -4.620e-03 -1.007e-03
2N2 4.488e-03 1.623e+02 1.366e-03 -4.275e-03
sig1 4.369e-03 2.239e+02 -3.028e-03 -3.149e-03
1S1k.3 4.187e-03 1.880e+02 -5.815e-04 -4.146e-03
phi1 4.004e-03 2.041e+02 -1.636e-03 -3.655e-03
1M1S.4 3.562e-03 3.195e+02 -2.315e-03 2.707e-03
L2 3.224e-03 7.157e+01 3.059e-03 1.019e-03
T2 3.214e-03 8.496e+01 3.202e-03 2.825e-04
pi1 3.203e-03 1.583e+02 1.186e-03 -2.975e-03
OO1 2.926e-03 2.115e+02 -1.530e-03 -2.494e-03
M3 2.552e-03 3.351e+02 -1.075e-03 2.315e-03
1M.1p1 2.537e-03 2.034e+02 -1.007e-03 -2.329e-03
the1 2.150e-03 1.751e+02 1.818e-04 -2.142e-03
1M1N.1S2 2.069e-03 1.529e+02 9.426e-04 -1.842e-03
1S.1o1 2.068e-03 2.371e+02 -1.737e-03 -1.123e-03
1M1N.4 1.720e-03 2.342e+02 -1.396e-03 -1.006e-03
nu2 1.715e-03 1.777e+02 6.774e-05 -1.714e-03
chi1 1.643e-03 1.640e+02 4.518e-04 -1.579e-03
lam2 1.516e-03 7.894e+01 1.488e-03 2.909e-04
psi1 1.488e-03 2.065e+02 -6.637e-04 -1.331e-03
1M1k.3 1.420e-03 2.494e+02 -1.329e-03 -5.005e-04
1M1o.3 1.203e-03 1.766e+02 7.126e-05 -1.200e-03
1M1K.4 1.061e-03 3.135e+02 -7.700e-04 7.298e-04
M6 1.003e-03 9.132e+01 1.003e-03 -2.310e-05
1k1j.2 9.816e-04 2.485e+02 -9.130e-04 -3.604e-04
S4 8.206e-04 2.562e+02 -7.970e-04 -1.957e-04
1o1p.2 7.511e-04 9.861e+01 7.426e-04 -1.125e-04
1S1o.3 7.233e-04 2.421e+02 -6.390e-04 -3.389e-04
1S1K.4 6.178e-04 3.552e+02 -5.119e-05 6.157e-04
1S1N.4 5.943e-04 3.198e+02 -3.839e-04 4.537e-04
1M1K.1S2 4.728e-04 2.021e+02 -1.775e-04 -4.382e-04
2M1N.6 4.564e-04 2.785e+01 2.132e-04 4.035e-04
2M1S.6 3.693e-04 1.740e+02 3.853e-05 -3.673e-04
2S.1M2 3.260e-04 3.177e+02 -2.193e-04 2.412e-04
1M1S.1N2 2.937e-04 2.796e+02 -2.896e-04 4.923e-05
1M1S1N.6 2.374e-04 7.091e+01 2.243e-04 7.762e-05
2M1K.6 1.883e-04 2.236e+02 -1.300e-04 -1.363e-04
R2 1.510e-04 5.277e+01 1.202e-04 9.136e-05
1o1q.2 1.308e-04 2.347e+02 -1.068e-04 -7.551e-05
2S1M.6 9.646e-05 2.971e+02 -8.586e-05 4.396e-05
1M1S1K.6 5.281e-05 3.579e+02 -1.976e-06 5.277e-05
Call:
lm(formula = x ~ -1 + ., data = xmat, na.action = na.exclude)
Form Factor: 2.990834
Features (Diurnal or Mixed):
MLLW MHLW MSL MLHW MHHW
0.4672917 0.5720560 0.8108796 1.0497033 1.1544676
Harmonics:
amplitude phase sine cosine
K1 0.173216 197.358105 -0.051678 -0.165327
O1 0.117990 214.371675 -0.066612 -0.097388
P1 0.054626 190.289438 -0.009757 -0.053747
M2 0.052382 109.620961 0.049341 -0.017590
S2 0.044984 87.978310 0.044956 0.001587
N2 0.015720 173.539053 0.001769 -0.015620
K2 0.014007 80.526441 0.013816 0.002306
TideHarmonics documentation built on May 2, 2019, 6:34 a.m.
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Description Usage Arguments Details Value See Also Examples
Description
Fit tidal data using any of over 400 harmonic constituents. Daily nodal corrections and time-varying mean sea-levels can be used.
Usage
1 2 |
Arguments
x |
A numeric vector or time series object giving the sea-levels. Missing values are allowed. |
dto |
A date/time vector of the same length as |
hcn |
A vector of constituent names. Some in-built vectors of names can be used: hc4, hc7, hc37, hc60 and hc114. If not specified, the vector hc60 is used by default. |
astlon |
The longitude formula to be used. The default "task" is the formulas use in the TASK-2000 software. The alternative "cartwright" uses Cartwright(1982). |
nodal |
Should nodal corrections be be used? |
smsl |
If |
span, degree |
Arguments passed to the loess function. |
... |
Passed to the linear model function |
Details
The function first removes the mean sea-level from the data (which by default is a single number) and the fits a linear model without intercept to sine and cosine terms defined by the specified harmonics. This (by default) includes nodal corrections. The sine and cosine coefficients can then be used to derive the amplitude and phases. See the package vignette for details.
Different names are used by various organizations for identical constituents. This package is designed to be robust, so that any common name can be used. In the output, the name will get converted to the set of names that we employ.
For constituents based on underlying components, we use our own
(logical) naming scheme rather than the (totally confusing)
historical scheme. See harmonics and the package
vignette for details. Either scheme should work for the input
vector hcn.
The UTC time zone is assumed by default. Even if a different
time zone is used, the phase lags will be calculated in UTC.
The utc argument of coef.tide can be used to
derive phase lags for different time zones.
An error will be produced if two specified harmonic components have virtually identical speeds (specifically, if the first five Doodson numbers are the same), even if the nodal corrections are different. This is to avoid numerical problems in the linear model fit, because these components will be difficult (or impossible) to identify separately.
The slowest harmonics in the default hc60 vector is the annual solar term Sa. If you do not have at least one year of data you should not include Sa. The fastest harmonics in hc60 have periods of just over 4 hours. If your frequency of observation is more than 2 hours you should not include the faster constituents.
Value
A list object of class c('tide','lm'). This is exactly the
save as a standard lm object but with the following
additional components
fval |
The form factor, which in terms of amplitudes is calculated as (K1+O1)/(M2+S2). This component and the two components given below are only available if all four of these harmonics are included in the fit. |
features1 |
A vector of fitted features that are relevant for semi-diurnal sites. MLWS = Mean Low Water Springs. MLWN = Mean Low Water Neaps. MSL = Mean Sea-Level. MHWN = Mean High Water Neaps. MHWS = Mean High Water Springs. |
features2 |
A vector of fitted features that are relevant for diurnal or mixed semi-diurnal sites. MLLW = Mean Lower Low Water. MHLW = Mean Higher Low Water. MSL = Mean Sea-Level. MLHW = Mean Lower High Water. MHHW = Mean Higher High Water. |
cfmat |
A matrix of sine and cosine coefficients, in the
same order as the |
cfmat |
A matrix of amplitudes, phase lags, sine and cosine coefficients, ordered by decreasing amplitude. |
origin |
The POSIXct value used as the origin, which is in
the centre of the |
vn0 |
A named vector containing reference signals (equilibrium phases) in degrees for each harmonic constituent. |
msl |
The mean sea level, either a vector (if |
lobj |
The fitted loess object if |
nodal |
The nodal argument. |
astlon |
The astlon argument. |
See Also
harmonics, hc114, plot.tide, predict.tide
Examples
1 2 3 4 |
Example output
Call:
lm(formula = x ~ -1 + ., data = xmat, na.action = na.exclude)
Form Factor: 2.991049
Features (Diurnal or Mixed):
MLLW MHLW MSL MLHW MHHW
0.4676174 0.5723951 0.8113304 1.0502657 1.1550435
Harmonics:
amplitude phase sine cosine
K1 1.733e-01 1.973e+02 -5.147e-02 -1.655e-01
O1 1.181e-01 2.144e+02 -6.673e-02 -9.738e-02
Sa 9.930e-02 4.774e+01 7.350e-02 6.678e-02
P1 5.462e-02 1.903e+02 -9.720e-03 -5.375e-02
M2 5.239e-02 1.096e+02 4.936e-02 -1.757e-02
S2 4.501e-02 8.800e+01 4.498e-02 1.573e-03
Q1 2.956e-02 2.191e+02 -1.865e-02 -2.293e-02
Mf 2.300e-02 3.561e+02 -1.567e-03 2.294e-02
S1 2.223e-02 3.306e+02 -1.092e-02 1.936e-02
Ssa 1.998e-02 1.629e+02 5.862e-03 -1.910e-02
N2 1.582e-02 1.733e+02 1.833e-03 -1.571e-02
K2 1.398e-02 8.040e+01 1.378e-02 2.331e-03
Mm 1.073e-02 4.210e+01 7.196e-03 7.963e-03
J1 1.037e-02 2.058e+02 -4.523e-03 -9.337e-03
mu2 7.204e-03 1.682e+02 1.476e-03 -7.051e-03
MSf 6.632e-03 1.454e+02 3.766e-03 -5.458e-03
2Q1 5.091e-03 2.221e+02 -3.414e-03 -3.777e-03
rho1 4.946e-03 2.101e+02 -2.481e-03 -4.279e-03
M4 4.730e-03 2.686e+02 -4.729e-03 -1.124e-04
M1 4.728e-03 2.577e+02 -4.620e-03 -1.007e-03
2N2 4.488e-03 1.623e+02 1.366e-03 -4.275e-03
sig1 4.369e-03 2.239e+02 -3.028e-03 -3.149e-03
1S1k.3 4.187e-03 1.880e+02 -5.815e-04 -4.146e-03
phi1 4.004e-03 2.041e+02 -1.636e-03 -3.655e-03
1M1S.4 3.562e-03 3.195e+02 -2.315e-03 2.707e-03
L2 3.224e-03 7.157e+01 3.059e-03 1.019e-03
T2 3.214e-03 8.496e+01 3.202e-03 2.825e-04
pi1 3.203e-03 1.583e+02 1.186e-03 -2.975e-03
OO1 2.926e-03 2.115e+02 -1.530e-03 -2.494e-03
M3 2.552e-03 3.351e+02 -1.075e-03 2.315e-03
1M.1p1 2.537e-03 2.034e+02 -1.007e-03 -2.329e-03
the1 2.150e-03 1.751e+02 1.818e-04 -2.142e-03
1M1N.1S2 2.069e-03 1.529e+02 9.426e-04 -1.842e-03
1S.1o1 2.068e-03 2.371e+02 -1.737e-03 -1.123e-03
1M1N.4 1.720e-03 2.342e+02 -1.396e-03 -1.006e-03
nu2 1.715e-03 1.777e+02 6.774e-05 -1.714e-03
chi1 1.643e-03 1.640e+02 4.518e-04 -1.579e-03
lam2 1.516e-03 7.894e+01 1.488e-03 2.909e-04
psi1 1.488e-03 2.065e+02 -6.637e-04 -1.331e-03
1M1k.3 1.420e-03 2.494e+02 -1.329e-03 -5.005e-04
1M1o.3 1.203e-03 1.766e+02 7.126e-05 -1.200e-03
1M1K.4 1.061e-03 3.135e+02 -7.700e-04 7.298e-04
M6 1.003e-03 9.132e+01 1.003e-03 -2.310e-05
1k1j.2 9.816e-04 2.485e+02 -9.130e-04 -3.604e-04
S4 8.206e-04 2.562e+02 -7.970e-04 -1.957e-04
1o1p.2 7.511e-04 9.861e+01 7.426e-04 -1.125e-04
1S1o.3 7.233e-04 2.421e+02 -6.390e-04 -3.389e-04
1S1K.4 6.178e-04 3.552e+02 -5.119e-05 6.157e-04
1S1N.4 5.943e-04 3.198e+02 -3.839e-04 4.537e-04
1M1K.1S2 4.728e-04 2.021e+02 -1.775e-04 -4.382e-04
2M1N.6 4.564e-04 2.785e+01 2.132e-04 4.035e-04
2M1S.6 3.693e-04 1.740e+02 3.853e-05 -3.673e-04
2S.1M2 3.260e-04 3.177e+02 -2.193e-04 2.412e-04
1M1S.1N2 2.937e-04 2.796e+02 -2.896e-04 4.923e-05
1M1S1N.6 2.374e-04 7.091e+01 2.243e-04 7.762e-05
2M1K.6 1.883e-04 2.236e+02 -1.300e-04 -1.363e-04
R2 1.510e-04 5.277e+01 1.202e-04 9.136e-05
1o1q.2 1.308e-04 2.347e+02 -1.068e-04 -7.551e-05
2S1M.6 9.646e-05 2.971e+02 -8.586e-05 4.396e-05
1M1S1K.6 5.281e-05 3.579e+02 -1.976e-06 5.277e-05
Call:
lm(formula = x ~ -1 + ., data = xmat, na.action = na.exclude)
Form Factor: 2.990834
Features (Diurnal or Mixed):
MLLW MHLW MSL MLHW MHHW
0.4672917 0.5720560 0.8108796 1.0497033 1.1544676
Harmonics:
amplitude phase sine cosine
K1 0.173216 197.358105 -0.051678 -0.165327
O1 0.117990 214.371675 -0.066612 -0.097388
P1 0.054626 190.289438 -0.009757 -0.053747
M2 0.052382 109.620961 0.049341 -0.017590
S2 0.044984 87.978310 0.044956 0.001587
N2 0.015720 173.539053 0.001769 -0.015620
K2 0.014007 80.526441 0.013816 0.002306
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