# Fan Plot of Forecast Distributions

`fanplot.Rd`

The `fanplot()`

function in surveillance wraps functionality of
the dedicated fanplot package, employing a different default style
and optionally adding point predictions and observed values.

## Arguments

- quantiles
a time x

`probs`

matrix of forecast quantiles at each time point.- probs
numeric vector of probabilities with values between 0 and 1.

- means
(optional) numeric vector of point forecasts.

- observed
(optional) numeric vector of observed values.

- start
time index (x-coordinate) of the first prediction.

- fan.args
a list of graphical parameters for the

`fan`

, e.g., to employ a different`colorRampPalette`

as`fan.col`

, or to enable contour lines via`ln`

.- means.args
a list of graphical parameters for

`lines`

to modify the plotting style of the`means`

. The default is a white line within the fan.- observed.args
a list of graphical parameters for

`lines`

to modify the plotting style of the`observed`

values.- key.args
if a list, a color key (in

`fan()`

's`"boxfan"`

-style) is added to the fan chart. The list may include positioning parameters`start`

(the x-position) and`ylim`

(the y-range of the color key),`space`

to modify the width of the boxfan, and`rlab`

to modify the labels. An alternative way of labeling the quantiles is via the argument`ln`

in`fan.args`

.- xlim,ylim
axis ranges.

- log
a character string specifying which axes are to be logarithmic, e.g.,

`log="y"`

(see`plot.default`

).- xlab,ylab
axis labels.

- add
logical indicating if the fan plot should be added to an existing plot.

- ...
further arguments are passed to

`plot.default`

. For instance,`panel.first`

could be used to initialize the plot with`grid(nx=NA, ny=NULL)`

lines.

## See also

the underlying `fan`

function in package
fanplot.
The function is used in `plot.oneStepAhead`

and
`plot.hhh4sims`

.

## Examples

```
## artificial data example to illustrate the graphical options
if (requireNamespace("fanplot")) {
means <- c(18, 19, 20, 25, 26, 35, 34, 25, 19)
y <- rlnorm(length(means), log(means), 0.5)
quantiles <- sapply(1:99/100, qlnorm, log(means), seq(.5,.8,length.out=length(means)))
## default style with point predictions, color key and log-scale
fanplot(quantiles = quantiles, probs = 1:99/100, means = means,
observed = y, key.args = list(start = 1, space = .3), log = "y")
## with contour lines instead of a key, and different colors
pal <- colorRampPalette(c("darkgreen", "gray93"))
fanplot(quantiles = quantiles, probs = 1:99/100, observed = y,
fan.args = list(fan.col = pal, ln = c(5,10,25,50,75,90,95)/100),
observed.args = list(type = "b", pch = 19))
}
```