Plot series of filled hexagons in ggplot2

Question

I am trying to create a tesselation of filled hexagons (polygons centered around a hexagonally-spaced lattice) in ggplot2. I have accomplished this using the 'plot' command but am struggling transitioning this to ggplot. Here is the code for the set-up: ``` # Generate a lattice of points equally spaced in the centers of a hexagonal lattice dist = 1 # distance between the centers of hexagons nx = dist*15 # horizontal extent ny = dist*15 # vertical extent MakeHexLattice = function(nx, ny, dist, origin=c(0,0)) { locations = cbind(location = 1:(nx*ny), x = sort(c(rep(seq(from=0, by=dist, length.out=nx),each=ceiling(ny/2)), rep(seq(from=dist/2, by=dist, length.out=nx), each=floor(ny/2)))) + origin[1], y = rep(c(seq(from=0, by = dist*sqrt(3), length.out=ceiling(ny/2)), seq(from=dist*sqrt(3)/2, by=dist*sqrt(3), length.out=floor(ny/2))) + origin[2], times=nx)) class(locations) = c(class(locations), "lattice") attr(locations, "gridsize") = dist return(locations) } ``` Here is the code for crea…

Accepted Answer

As with most things in ggplot, the plotting is actually extremely straightforward, most of the work is getting your data in the right shape so that it makes sense. A `for` loop is entirely unnecessary, `geom_polygon()` just needs a dataframe with the x and y coordinates, and a variable defining which group they belong to. With your data:

```
library(ggplot2)
library(reshape2)

#Get your coordinates in long format with an id
hexdat.x <- melt(cbind(id = 1:length(hex.x), as.data.frame(hex.x)), id.vars = "id", value.name = "x")
hexdat.y <- melt(cbind(id = 1:length(hex.y), as.data.frame(hex.y)), id.vars = "id", value.name = "y")

#Merge them into the same dataframe
hexdat <- merge(hexdat.x, hexdat.y)

head(hexdat)
#   id variable    x          y
# 1  1       V1  0.0 -0.5773503
# 2  1       V2  0.5 -0.2886751
# 3  1       V3  0.5  0.2886751
# 4  1       V4  0.0  0.5773503
# 5  1       V5 -0.5  0.2886751
# 6  1       V6 -0.5 -0.2886751
```

Now to plot the hexagons, you just need to give `ggplot` the x and y coordinates, and specify the group each one belongs to:

```
ggplot(hexdat, aes(x, y)) + 
  geom_polygon(aes(group = id), fill = "wheat", colour = "black")
```

Plot series of filled hexagons in ggplot2

Solution

Problem