plot.uvevd | R Documentation |
Four plots (selectable by which
) are currently provided:
a P-P plot, a Q-Q plot, a density plot and a return level plot.
## S3 method for class 'uvevd'
plot(x, which = 1:4, main, ask = nb.fig <
length(which) && dev.interactive(), ci = TRUE, cilwd = 1,
a = 0, adjust = 1, jitter = FALSE, nplty = 2, ...)
## S3 method for class 'gumbelx'
plot(x, interval, which = 1:4, main, ask = nb.fig <
length(which) && dev.interactive(), ci = TRUE, cilwd = 1,
a = 0, adjust = 1, jitter = FALSE, nplty = 2, ...)
x |
An object that inherits from class |
which |
If a subset of the plots is required, specify a
subset of the numbers |
main |
Title of each plot. If given, must be a character
vector with the same length as |
ask |
Logical; if |
ci |
Logical; if |
cilwd |
Line width for confidence interval lines. |
a |
Passed through to |
adjust , jitter , nplty |
Arguments to the density plot.
The density of the fitted model is plotted with a rug plot and
(optionally) a non-parameteric estimate. The argument
|
interval |
A vector of length two, for the gumbelx (maximum of two Gumbels) model. This is passed to the uniroot function to calculate quantiles for the Q-Q and return level plots. The interval should be large enough to contain all plotted quantiles or an error from uniroot will occur. |
... |
Other parameters to be passed through to plotting functions. |
The following discussion assumes that the fitted model is stationary. For non-stationary generalized extreme value models the data are transformed to stationarity. The plot then corresponds to the distribution obtained when all covariates are zero.
The P-P plot consists of the points
\{(G_n(z_i), G(z_i)), i = 1,\ldots,m\}
where G_n
is the empirical distribution function
(defined using ppoints
), G is the model based
estimate of the distribution (generalized extreme value
or generalized Pareto), and z_1,\ldots,z_m
are the data
used in the fitted model, sorted into ascending order.
The Q-Q plot consists of the points
\{(G^{-1}(p_i), z_i), i = 1,\ldots,m\}
where G^{-1}
is the model based estimate of the quantile
function (generalized extreme value or generalized Pareto),
p_1,\ldots,p_m
are plotting points defined by
ppoints
, and z_1,\ldots,z_m
are the data
used in the fitted model, sorted into ascending order.
The return level plot for generalized extreme value models is defined as follows.
Let G
be the generalized extreme value distribution
function, with location, scale and shape parameters a
,
b
and s
respectively.
Let z_t
be defined by G(z_t) = 1 - 1/t
.
In common terminology, z_t
is the return level
associated with the return period t
.
Let y_t = -1/\log(1 - 1/t)
.
It follows that
z_t = a + b(y_t^s - 1)/s.
When s = 0
, z_t
is defined by continuity, so that
z_t = a + b\log(y_t).
The curve within the return level plot is z_t
plotted
against y_t
on a logarithmic scale, using maximum likelihood
estimates of (a,b,s)
. If the estimate of s
is zero, the
curve will be linear.
For large values of t
, y_t
is approximately equal
to the return period t
. It is usual practice to label the
x-axis as the return period.
The points on the plot are
\{(-1/\log(p_i), z_i), i = 1,\ldots,m\}
where p_1,\ldots,p_m
are plotting points defined by
ppoints
, and z_1,\ldots,z_m
are the data
used in the fitted model, sorted into ascending order.
For a good fit the points should lie “close” to the curve.
The return level plot for peaks over threshold models is defined as follows.
Let G
be the generalized Pareto distribution function,
with location, scale and shape parameters u
, b
and s
respectively, where u
is the model threshold.
Let z_m
denote the m
period return level
(see fpot
and the notation therein).
It follows that
z_m = u + b((pmN)^s - 1)/s.
When s = 0
, z_m
is defined by continuity, so that
z_m = u + b\log(pmN).
The curve within the return level plot is z_m
plotted
against m
on a logarithmic scale, using maximum likelihood
estimates of (b,s,p)
. If the estimate of s
is zero,
the curve will be linear.
The points on the plot are
\{(1/(pN(1-p_i)), z_i), i = 1,\ldots,m\}
where p_1,\ldots,p_m
are plotting points defined by
ppoints
, and z_1,\ldots,z_m
are the data
used in the fitted model, sorted into ascending order.
For a good fit the points should lie “close” to the curve.
plot.bvevd
, density
,
jitter
, rug
, ppoints
uvdata <- rgev(100, loc = 0.13, scale = 1.1, shape = 0.2)
M1 <- fgev(uvdata)
## Not run: par(mfrow = c(2,2))
## Not run: plot(M1)
uvdata <- rgpd(100, loc = 0, scale = 1.1, shape = 0.2)
M1 <- fpot(uvdata, 1)
## Not run: par(mfrow = c(2,2))
## Not run: plot(M1)
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