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Draw thematic map on an Optimal Channel Network

draw_thematic_OCN.Rd

Function that draws OCNs with color of RN or AG nodes depending on an arbitrary theme.

Usage

draw_thematic_OCN(OCN,theme=NA*numeric(OCN$AG$nNodes),
  chooseAggregation = NULL,
  discreteLevels = FALSE, 
  colLevels = NULL, cutoff = FALSE,
  colPalette = colorRampPalette(c("yellow","red","black")),
  exactDraw = FALSE, chooseCM = FALSE, drawNodes = FALSE,  
  nodeType = "upstream",  nanColor = "#00BFFF",
  riverColor = "#00BFFF", backgroundColor = "#999999", 
  addLegend = TRUE, min_lwd = 0.5, max_lwd = 5, 
  add = FALSE, args_imagePlot = list(), args_legend = list(), 
  ...)

Arguments

OCN

A river object as produced by aggregate_OCN. The order of arguments between OCN and theme can be swapped freely.

theme

Vector (of length OCN$AG$Nnodes or OCN$RN$Nnodes) expressing the spatial field of interest. The vector can contain NA and NaN values to identify RN or AG nodes where the theme is not defined. The order of arguments between OCN and theme can be swapped freely.

chooseAggregation

Only effective if OCN$RN$nNodes == OCN$AG$nNodes. In such case, it must be equal to either "RN" or "AG"; as a result, theme will be interpreted as a spatial field in the corresponding aggregation level. Default is "AG".

discreteLevels

Logical. If FALSE, a continuous color scheme is used. If TRUE, discrete color levels are applied. See also colLevels and examples.

colLevels

Number of colors in the palette. If discreteLevels == FALSE, colLevels must be a vector of the form c(minval, maxval) or c(minval, maxval, N_levels). The vector of breakpoints used to attribute theme values to a given color is then defined as seq(minval, maxval, N_levels). Default is minval = min(theme[!(is.nan(theme))]), maxval = max(theme[!(is.nan(theme))]), N_levels = 1000. If discreteLevels == TRUE and is.null(colLevels) == TRUE, each unique value of theme is attributed a different color. If discreteLevels == TRUE and colLevels is a vector, colLevels is used as vector of breakpoints. In this case, the number of discrete colors is equal to length(colLevels) - 1.

cutoff

Logical. If FALSE, nodes whose theme value is beyond the range established by the vector of breakpoints are attributed the color corresponding to the lowest (or highest) value in the color scheme. If TRUE, such nodes are attributed the color NaNcolor.

colPalette

Color palette used to display theme values. colPalette accepts both functions creating color palettes and vectors of colors. In the latter case, length(colPalette) must be greater than the number of color levels. See examples below and hcl.colors.

chooseCM

Index of catchment to display (only effective if OCN$nOutlet > 1). It can be a logical or a numeric vector. If FALSE, all catchments are displayed. If TRUE, the catchment with largest area is displayed. If chooseCM is a subset of vector 1:length(OCN$nOutlet), only the catchment(s) identified by the indices in chooseCM are displayed.

exactDraw

Logical. If TRUE, the real shape of OCNs is plotted. If flow crosses a boundary, the pixel that is not contiguous to its outlet is flipped.

drawNodes

Logical. If FALSE, the theme is directly displayed on the river network. In this case, the edge departing from a given node is displayed with the color attributed to the node. If TRUE, the theme is displayed via markers at the locations of the nodes at the RN or AG level (depending on the length of theme). In this case, nanColor can be used to define the color of the river network.

nodeType

Only effective if drawNodes == TRUE and length(theme) == OCN$RN$nNodes. Can assume values "upstream" or "downstream". If "upstream", nodes are drawn at the upstream ends of the corresponding edges (i.e. at the coordinates defined by OCN$AG$X, OCN$AG$Y). If "downstream", nodes are drawn at the downstream ends of the corresponding edges (i.e. at the coordinates defined by OCN$AG$XReach, OCN$AG$YReach).

nanColor

Color attributed to RN or AG nodes whose theme value is NA or NaN.

riverColor

Only effective if drawNodes == TRUE or if theme is a vector of NA values (as in the default option). Color used to display the OCN below the nodes.

backgroundColor

Color used in the background of the figure. It can be either a single value, or a vector with number of components equal to length(chooseCM). If length(backgroundColor) == length(chooseCM), each color is used to identify a different catchment selected in chooseCM (corresponding to the respective outlet). If instead length(chooseCM) > 1 and length(backgroundColor) == 1, all catchments are colored with the same backgroundColor.

addLegend

Logical. If TRUE, add legend to the plot. If also discreteLevels = FALSE, image.plot is used to display the legend, which appears as a colorbar; as a result, elements (e.g. node coordinates) subsequently plotted of on top of the 2D elevation map might be wrongly positioned.

min_lwd, max_lwd

Minimum and maximum values of line width used to display the OCN (actual line width is proportional to the square root of drainage area).

add

Logical. If TRUE, add to an already existing plot. Taken as FALSE (with a warning if a different value is supplied) if no graphics device is open.

args_imagePlot

Only effective if addLegend = TRUE and discreteLevels = FALSE. List of arguments passed to imagePlot for drawing a continuous legend. For example, argument smallplot can be used to specify the plot coordinates for the legend.

args_legend

Only effective if addLegend = TRUE and discreteLevels = TRUE. List of arguments passed to legend for drawing a discrete legend.

...

Further arguments to be passed to plot.

Value

No output is returned.

Details

This function can be used to show how a certain spatial field varies along the river network.

Default plot options. By default, it is set asp = 1, xlab = "", ylab = "". If at least one between xlim and ylim is specified by the user, the default for axes is TRUE, and is FALSE if not. Specifying xlim and ylim helps zoom into a portion of the river network; however, due to the default asp = 1, the displayed region might be larger than what is expected if the ranges of xlim and ylim are different. To avoid this, set asp = NA (at the cost of producing a deformed river network).

Adding scale bar and north arrow. Scale bar and north arrow can be added via terra's functions sbar and north, respectively. However, note that arguments d and xy must be specified by the user (because no rast object is plotted). See example 5.

Examples

# 1a) Six different ways to display contributing area at the AG level
OCN <- aggregate_OCN(landscape_OCN(OCN_20), thrA = 4)
old.par <- par(no.readonly = TRUE)
par(mfrow=c(2,3), oma = c(0, 0, 3, 0))
draw_thematic_OCN(OCN$AG$A, OCN, colPalette = hcl.colors) 
title("Continuous levels \n Colors on edges")
draw_thematic_OCN(OCN$AG$A, OCN, discreteLevels = TRUE,
    colPalette = hcl.colors) 
title("Discrete, unique levels \n Colors on edges")
draw_thematic_OCN(OCN$AG$A, OCN, discreteLevels = TRUE, 
    colLevels = c(1, 10, 50, 100, 500), 
    colPalette = hcl.colors) 
title("Discrete, user-defined levels \n Colors on edges")
draw_thematic_OCN(OCN$AG$A, OCN, drawNodes = TRUE, 
    colPalette = hcl.colors)
title("Continuous levels \n Colors on edges")
draw_thematic_OCN(OCN$AG$A, OCN,  discreteLevels = TRUE, 
    drawNodes = TRUE, colPalette = hcl.colors)
title("Discrete, unique levels \n Colors on nodes")
draw_thematic_OCN(OCN$AG$A, OCN, discreteLevels = TRUE, 
    drawNodes = TRUE, colLevels = c(1, 10, 50, 100, 500), 
    colPalette = hcl.colors)
title("Discrete, user-defined levels \n Colors on nodes")
mtext("Six different ways to display contributing area [no. pixels]", outer = TRUE, cex = 1.5)

par(old.par)

# 1b) Same as above, but use different colLevels, cutoff combinations
# with DiscreteLevels = FALSE
old.par <- par(no.readonly = TRUE)
par(mfrow=c(1,2))
draw_thematic_OCN(OCN$AG$A, OCN, drawNodes = TRUE,
     colLevels = c(0, 200, 1000), colPalette = hcl.colors)
title("All nodes with A > 200 pixels \n are displayed in yellow")
draw_thematic_OCN(OCN$AG$A, OCN, drawNodes = TRUE, 
    nanColor = "#00000000", colLevels = c(0, 200, 1000),
    cutoff = TRUE, colPalette = hcl.colors)
title("All nodes with A > 200 pixels \n are treated as NaN")    

par(old.par)

if (FALSE) {
# 2) Display distance to outlet (at the RN level) along the main stem
# of an OCN
OCN <- aggregate_OCN(landscape_OCN(OCN_250_T)) # this takes some seconds
OCN <- paths_OCN(OCN, includePaths = TRUE) # this takes some seconds

distanceToOutlet <- OCN$RN$downstreamPathLength[,OCN$RN$outlet]
farthestNode <- which(distanceToOutlet == max(distanceToOutlet))
mainStem <- OCN$RN$downstreamPath[[farthestNode]][[OCN$RN$outlet]]
theme <- rep(NaN, OCN$RN$nNodes)
theme[mainStem] <- distanceToOutlet[mainStem]

draw_thematic_OCN(theme, OCN)
title("Distance to outlet along the main stem [pixel units]")
}

# 3) Show an OCN without a theme
OCN <- aggregate_OCN(landscape_OCN(OCN_20), thrA = 4)
draw_thematic_OCN(OCN)

draw_thematic_OCN(OCN, xlim=c(3,8), ylim=c(0,5)) # zoom closer at the outlet


# 4) Adjust legend location
draw_thematic_OCN(OCN, OCN$AG$A, 
  args_imagePlot = list(smallplot = c(0.1, 0.11, 0.1, 0.3)))

draw_thematic_OCN(OCN, OCN$AG$streamOrder, 
  discreteLevels = TRUE, args_legend = list(x = -2, y = 1))


# 5) add thematic OCN on top of map and show scale bar and north arrow
draw_elev2D_OCN(OCN)
draw_thematic_OCN(OCN, OCN$AG$slope, backgroundColor = NULL, 
add = TRUE, colPalette = hcl.colors(1000, "Grays", rev = TRUE),
args_imagePlot = list(smallplot=c(0.05,0.07,0.1,0.9)))
# now add scale bar and north arrow
library(terra)
#> terra 1.7.71
# sbar() # this would throw an error
# north()# this would throw an error
sbar(d=1, xy=c(min(OCN$FD$X), min(OCN$FD$Y)-1)) # this works
north(d=1, xy=c(max(OCN$FD$X)+1, max(OCN$FD$Y))) # this works