plot.cube: Plot a gdalcubes data cube

In gdalcubes: Earth Observation Data Cubes from Satellite Image Collections

Plot a gdalcubes data cube

Description

Plot a gdalcubes data cube

Usage

## S3 method for class 'cube'
plot(
  x,
  y,
  ...,
  nbreaks = 11,
  breaks = NULL,
  col = grey(1:(nbreaks - 1)/nbreaks),
  key.pos = NULL,
  bands = NULL,
  t = NULL,
  rgb = NULL,
  zlim = NULL,
  gamma = 1,
  periods.in.title = TRUE,
  join.timeseries = FALSE,
  axes = TRUE,
  ncol = NULL,
  nrow = NULL,
  downsample = TRUE,
  na.color = "#AAAAAA"
)

Arguments

x	a data cube proxy object (class cube)
y	__not used__
...	further arguments passed to image.default
nbreaks	number of breaks, should be one more than the number of colors given
breaks	actual breaks used to assign colors to values; if missing, the function subsamples values and uses equally sized intervals between min and max or zlim[0] and zlim[1] if defined
col	color definition, can be a character vector with nbreaks - 1 elements or a function such as heat.colors
key.pos	position for the legend, 1 (bottom), 2 (left), 3 (top), or 4 (right). If NULL (the default), do not plot a legend.
bands	integer vector with band numbers to plot (this must be band numbers, not band names)
t	integer vector with time indexes to plot (this must be time indexes, not date / time)
rgb	bands used to assign RGB color channels, vector of length 3 (this must be band numbers, not band names)
zlim	vector of length 2, defining the minimum and maximum values to either derive breaks, or define black and white values in RGB plots
gamma	gamma correction value, used for RGB plots only
periods.in.title	logical value, if TRUE, the title of plots includes the datetime period length as ISO 8601 string
join.timeseries	logical, for pure time-series plots, shall time series of multiple bands be plotted in a single plot (with different colors)?
axes	logical, if TRUE, plots include axes
ncol	number of columns for arranging plots with layout(), see Details
nrow	number of rows for arranging plots with layout(), see Details
downsample	length-one integer or logical value used to select only every i-th pixel (in space only) for faster plots; by default (TRUE), downsampling will be determined automatically based on the resolution of the graphics device; set to FALSE to avoid downsampling.
na.color	color used to plot NA pixels

Details

The style of the plot depends on provided parameters and on the shape of the cube, i.e., whether it is a pure time series and whether it contains multiple bands or not. Multi-band, multi-temporal images will be arranged with layout() such that bands are represented by columns and time is represented by rows. Time series plots can be combined to a single plot by setting join.timeseries = TRUE. The layout can be controlled with ncol and nrow, which define the number of rows and columns in the plot layout. Typically, only one of ncol and nrow is provided. For multi-band, multi-temporal plots, the actual number of rows or columns can be less if the input cube has less bands or time slices.

The downsample argument is used to speed-up plotting if the cube has much more pixels than the graphics device. If set to a scalar integer value > 1, the value is used to skip pixels in the spatial dimensions. For example, setting downsample = 4 means that every fourth pixel is used in the spatial dimensions. If TRUE (the default) downsample is derived automatically based on the sizes of the cube and the graphics device. If 1 or FALSE, no additional downsampling is performed. Notice that downsampling is only used for plotting. The size of the data cube (and hence the computation time to process the data cube) is not modified.

Note

If caching is enabled for the package (see gdalcubes_options), repeated calls of plot for the same data cube will not reevaluate the cube. Instead, the temporary result file will be reused, if possible.

Some parts of the function have been copied from the stars package (c) Edzer Pebesma

Examples

# create image collection from example Landsat data only 
# if not already done in other examples
if (!file.exists(file.path(tempdir(), "L8.db"))) {
  L8_files <- list.files(system.file("L8NY18", package = "gdalcubes"),
                         ".TIF", recursive = TRUE, full.names = TRUE)
  create_image_collection(L8_files, "L8_L1TP", file.path(tempdir(), "L8.db"), quiet = TRUE) 
}

L8.col = image_collection(file.path(tempdir(), "L8.db"))
v = cube_view(extent=list(left=388941.2, right=766552.4, 
              bottom=4345299, top=4744931, t0="2018-04", t1="2018-06"),
              srs="EPSG:32618", nx = 497, ny=526, dt="P1M")
              
plot(select_bands(raster_cube(L8.col, v), c("B02", "B03", "B04")), rgb=3:1)
              
L8.cube = select_bands(raster_cube(L8.col, v), c("B04", "B05")) 
L8.ndvi = apply_pixel(L8.cube, "(B05-B04)/(B05+B04)", "NDVI") 
plot(reduce_time(L8.ndvi, "median(NDVI)"), key.pos=1, zlim=c(0,1))

gdalcubes documentation built on May 29, 2024, 5:11 a.m.