R: Horizon plots of Raster objects.

horizonplot-methods {rasterVis} | R Documentation

## Horizon plots of Raster objects.

### Description

This method draws horizon graphs for each zone as calculated with `zonal` from the directions defined by `xyLayer`

### Usage

    ## S4 method for signature 'RasterStackBrick,missing'
    horizonplot(x, data = NULL,
        dirXY = y, stat = 'mean', digits = 0,
        origin = mean,
        xlab = 'Time', ylab = 'direction',
        colorkey = TRUE, colorkey.digits = 1,
        scales=list(y = list(relation = "same")),
        ...)

### Arguments

`x` | A `RasterStackBrick` object.
`data` | Not used.
`dirXY` | A direction as a function of the coordinates (see `xyLayer`).
`stat` | a function to be applied to summarize the values by zone. See `zonal` for details.
`digits` | An integer, number of digits for `zonal`.
`origin` | From the `latticeExtra` help page: "the baseline y value for the first (positive) segment (i.e. the value at which red changes to blue)." It can be: a number, used acrros all panels, or a function (or a character defining a function), evaluated with the values in each panel. The default is the `mean` function.
`xlab, ylab` | Labels of the axis.
`colorkey` | If `colorkey = TRUE` a suitable color scale bar is constructed using the values of `origin` and `horizonscale` (see below). For additional information see `levelplot`.
`colorkey.digits` | Digits for rounding values in `colorkey` labels
`scales` | From the `lattice::xyplot` help page: "A list determining how the x- and y-axes (tick marks and labels) are drawn. The list contains parameters in `name=value` form, and may also contain two other lists called `x` and `y` of the same form. Components of `x` and `y` affect the respective axes only, while those in `scales` affect both. When parameters are specified in both lists, the values in `x` or `y` are used." In `horizonplot` the most interesting component is `relation`, a character string that determines how axis limits are calculated for each panel. Possible values are `"same"` (default), `"free"` and `"sliced"`. "For ‘relation="same"’, the same limits, usually large enough to encompass all the data, are used for all the panels. For ‘relation="free"’, limits for each panel is determined by just the points in that panel. Behavior for ‘relation="sliced"’ is similar, except that the length (max - min) of the scales are constrained to remain the same across panels."
`...` | Additional arguments for the `horizonplot` function. `horizonscale` is the most interesting, being (from the `latticeExtra` help page) "the scale of each color segment. There are 3 positive segments and 3 negative segments. If this is a given as a number then all panels will have comparable distances, though not necessarily the same actual values (similar in concept to ‘scales$relation = "sliced"’)". On the other hand, `col.regions` is used to choose the color scale.

### Details

(Extracted from the reference): "The horizon graph allows to examine how a large number of items changed through time, to spot extraordinary behaviors and predominant patterns, view each of the items independently from the others when they wish, make comparisons between the items, and view changes that occurred with enough precision to determine if further examination is required."

### References

http://www.perceptualedge.com/articles/visual_business_intelligence/time_on_the_horizon.pdf

### See Also

`horizonplot`, `xyplot`, `levelplot`.

### Examples

    ## Not run:
    library(zoo)

    url <- "ftp://ftp.wiley.com/public/sci_tech_med/spatio_temporal_data/"
    sst.dat = read.table(paste(url, "SST011970_032003.dat", sep=''), header = FALSE)
    sst.ll = read.table(paste(url, "SSTlonlat.dat", sep=''), header = FALSE)

    spSST <- SpatialPointsDataFrame(sst.ll, sst.dat)
    gridded(spSST) <- TRUE
    proj4string(spSST) = "+proj=longlat +datum=WGS84"
    SST <- brick(spSST)

    idx <- seq(as.Date('1970-01-01'), as.Date('2003-03-01'), by='month')
    idx <- as.yearmon(idx)
    SST <- setZ(SST, idx)
    names(SST) <- as.character(idx)

    horizonplot(SST)

    horizonplot(SST, stat='sd')

    ## Different scales for each panel, with colors representing deviations
    ## from the origin in *that* panel
    horizonplot(SST, scales=list('free'))

    ## origin may be a function...
    horizonplot(SST, origin=mean)
    ## ...or a number
    horizonplot(SST, origin=0)

    ## A different color palette
    horizonplot(SST, origin=0, col.regions=brewer.pal(n=6, 'PuOr'))

    ## The width of each color segment can be defined with horizonscale
    horizonplot(SST, horizonscale=1, origin=0)

    ## End(Not run)

    ## Not run:

    old <- getwd()
    ##change to your folder...
    setwd('CMSAF')
    listFich <- dir(pattern='2008')
    stackSIS <- stack(listFich)
    stackSIS <- stackSIS*24 ##from irradiance (W/m2) to irradiation Wh/m2
    setwd(old)

    idx <- seq(as.Date('2008-01-15'), as.Date('2008-12-15'), 'month')

    SISmm <- setZ(stackSIS, idx)
    names(SISmm) <- month.abb

    horizonplot(SISmm)

    ## End(Not run)

[Package rasterVis version 0.44 Index]