multigons {StratigrapheR}

Draws several polygons

Description

Draws several polygons. This function expands on the polygon() function from base R graphics. The difference is that several polygons can be drawn in one line by providing a polygon id: i. To each polygon you can provide different graphical parameters (i.e. colour, shading, etc). On the contrary of the polygon() function the graphical parameters of the shading lines can be independent of the border lines.

Usage

multigons(
  i,
  x,
  y,
  j = unique(i),
  forget = NULL,
  front = NULL,
  back = NULL,
  density = 0,
  angle = 45,
  border = "black",
  col = NA,
  lty = par("lty"),
  lwd = par("lwd"),
  scol = border,
  slty = lty,
  slwd = lwd,
  lend = 0,
  ljoin = 0,
  lmitre = 10
)

Arguments

i

a polygon id for each x and y coordinate, i.e. the name of each polygon. If you want to give each polygon a different aspect you should provide a vector of n elements (if you have three polygons "A1", "A2" and "A3" with "A2" that should be blue you should provide the colours of all three: e.g. col = c("white", "blue", "white"))

x, y

numeric vectors of x and y coordinates

j

a list of the ids (names) in the order used for the graphical parameters (e.g. colour, shading, etc...). By default they are in their order of appearance in i

forget

the polygons that should not be drawn, by their id or index (i.e. name or number of appearance).

front, back

the polygons to be put in front and back position, by their id or index (i.e. name or number of appearance). By default the order is the one defined by j, and if j is absent by the order in i.

density

the density of shading lines, in lines per inch. The default value of 0 means that no shading lines are drawn.

angle

the slope of shading lines, given as an angle in degrees (counter-clockwise).

border

the colour to draw the border. The default is black. Use border = NA to omit borders.

col

the colour for filling the polygon. The default, NA, is to leave polygons unfilled.

lty, lwd

the border line type and width, see ?par for details.

scol, slty, slwd

the colour, type and width of the shading lines.

lend, ljoin, lmitre

additional graphical parameters, see ?par for details.

Details

In the case you want shading this function will draw three overlapping polygons: one for the background, one for the shading lines and one for the border. multigons shares similarities with centresvg and framesvg, but allows more advanced control of each element.

See Also

Similar functions: multilines, infobar

Complementary function: shift

Uses ignore to avoid drawing unnecessary objects

Examples

# Simple use:

i <- c(rep("A1",6), rep("A2",6), rep("A3",6)) # Polygon ids
x <- c(1,2,3,3,2,1,2,3,4,4,3,2,3,4,5,5,4,3)   # x coordinates
y <- c(1,2,3,4,5,6,1,2,3,4,5,6,1,2,3,4,5,6)   # y coordinates

plot(c(-1,7), c(-2,9), type = "n", xlab = "", ylab = "", main = "Simple use")

multigons(i, x, y,
          front = "A2", # This gets the polygon A2 in front of all others
          density = c(NA, 5, 10),  # Different shading density
          scol = "darkred", # Same shading colour
          col = c("black", "grey", "white"), # Different background colour
          lwd = 2, # Width of border lines for all polygons
          slty = 2, # Shading lines type, same for all polygons
          slwd = 1) # Shading lines width, same for all polygons

# Advanced use:
# Lets first create more polygons

i2 <- c(i, rep("A4",6), rep("A5",6), rep("A6",6))
x2 <- rep(x,2)
y2 <- c(y, y - 4)

# Then lets attribute a group to each of them: lets say blue and red polygons

groups <- data.frame(j = c("A1", "A2", "A3", "A4", "A5","A6"),
                      group = c("blue", "red", "blue", "red", "red", "blue"),
                      stringsAsFactors = FALSE)

# Then lets attribute different graphical parameters for each group

legend <- data.frame(group = c("red", "blue"),
                     col = c("red", "blue"),
                     density = c(10,20),
                     scol = c("darkred", "darkblue"),
                      stringsAsFactors = FALSE)

 # Now that you have a data frame saying which polygon is in which group,
 # and one providing distinct graphical parameters for each group, you can
 # join the two with help of the dplyr package:

 library(dplyr)

 parameters <- left_join(groups, legend, by = "group")

 # Then simply apply them to multigons:

 plot(c(0,12), c(-3,7), type = "n", xlab = "", ylab = "",
      main = "Advanced use")

 multigons(i2,x2,y2,
           forget = c("A1"),     # If you want to avoid drawing one polygon
           front = c("A2","A3"), # Puts A2 in front and A3 right behind
           col = parameters$col,
           density = parameters$density,
           scol = parameters$scol,
           lwd = 2)

# Another way (more advanced, but with interesting programming applications)
# to code this:

all.parameters <- merge_list(list(i = i2, x = x2 + 6, y = y2),
                             as.list(parameters),
                             list(lwd = 3, slwd = 2, slty = 2))

all.parameters <- all.parameters[!names(all.parameters) == "group"]

do.call(multigons, all.parameters)