Load the packages and generate test dataset.
library(ggplot2)
library(grid)
df = data.frame(
x = rep(c(2, 5, 7, 9, 12), 2),
y = rep(c(1, 2), each = 5),
z = factor(rep(1:5, each = 2)),
w = rep(diff(c(0, 4, 6, 8, 10, 14)), 2)
)We make a “heatmap” with the ggplot2 package.
ggplot(df, aes(x, y)) +
geom_tile(aes(fill = z), color = NA)
Depends on the “graphics device” you use, you might see white vertical and horizontal lines between cells in the plot. Here in this example I use “svg”, but there is no such problem with other devices such as “png” or “jpeg”.
Of course you can remove color = NA to add borders for these cells. But you might see
One solution to remove such white lines
- obtain the cells
- for each cell, increase its width and height by 1 point on the four sides
ggplot(df, aes(x, y)) +
geom_tile(aes(fill = z), color = NA)
# making viewports available
grid.force()
# obtain the path of `geom_rect`
vpath = grid.grep("geom_rect", grobs = TRUE, viewports = TRUE, grep = TRUE)
# obtain the rect grobs
grect = grid.get(vpath)
# edit the grob by extending 1pt on both sides
grect$width = grect$width + unit(2, "pt")
grect$height = grect$height + unit(2, "pt")
# update the plot
grid.set(vpath, grect)