geom_tile in ggplot2 returning blank plot

Question

I am trying to plot a dataset with three columns using the code below, but I get a blank figure with just the names on the axis, can anyone tell me what I am doing wrong?

#rm(list=ls())
library(data.table)
library(wesanderson)
library(ggplot2)

exa <- fread("sample.csv", sep = "," ,header = T,  stringsAsFactors = FALSE)

pal <- wes_palette("Zissou1", 100, type = "continuous")
sp1<-ggplot(exa, aes(x=x, y=y, fill=z))+
geom_tile(show.legend = T)+
scale_fill_gradientn(colours = pal) + 
  scale_x_discrete(expand = c(0, 0)) +
  scale_y_discrete(expand = c(0, 0)) 
sp1

Data:

exa <- structure(list(x = c(0.457744, 0.492325, 0.49948, 0.471712, 0.504126, 
0.505528, 0.516318, 0.521419, 0.518354, 0.523001, 0.527301, 0.566585, 
0.411753, 0.427226, 0.446747, 0.43778, 0.432248, 0.444912, 0.462414, 
0.456952, 0.443462, 0.420683, 0.392057), y = c(25.69908, 25.65119, 
25.8332, 23.88982, 22.41502, 22.27553, 23.05898, 24.20714, 25.23666, 
25.35443, 25.78347, 27.20575, 20.94434, 21.62892, 22.61483, 22.49146, 
23.38523, 24.46414, 25.8023, 26.63754, 27.40164, 27.45981, 27.97814
), z = c(29.75408, 29.02752, 28.43744, 27.98952, 27.62504, 27.32658, 
27.04928, 26.77825, 26.53036, 26.28481, 26.04137, 25.80254, 28.5918, 
27.81994, 27.44201, 27.15059, 26.83333, 26.54576, 26.31531, 26.12999, 
25.88431, 25.65788, 25.47488)), class = "data.frame", row.names = c(NA, 
-23L))

ndichistan, I suggested an edit to your question that (a) comments out the previously-not-visible `rm(list=ls())`, it was not visible because your [markdown code-fence](https://stackoverflow.com/editing-help) was wrong, and please don't include code that "dangerous" so easily mis-run ..., and (b) removed the link to your data and replaced it *with the data*. If it's this small, it's much easier to just work with it here, and when links go stale (they almost always do), the question otherwise becomes unreproducible and less valuable to follow-on readers. Thanks! — r2evans, Jun 10 '20 at 23:09
I cannot reproduce your problem: while they are *small*, I do see splotches sparsely throughout the canvas. Could it be that you're looking on a small plot window and just can't see the dots? Is your "real" data much larger, therefore things are being subdued for other reasons? — r2evans, Jun 10 '20 at 23:13
Cannot reproduce either (although I didn't try your color pallete). — Axeman, Jun 10 '20 at 23:26
@r2evans Thanks so much for the edits and suggestions for future posting. I did not see the splotches (maybe for the reasons you suggested), unfortunately, I cannot disclose the full data. It is however a 3cols*48rows dataframe. Is there a way to make it more visible? — ndichistan, Jun 10 '20 at 23:47
@Axeman Thanks for your edits. Were you able to see the splotches? — ndichistan, Jun 10 '20 at 23:49
Yeah there's just small tiles. Are you sure you want tiles? They need evenly spaced data, which your data doesn't look like. Can't you just make colored points instead? — Axeman, Jun 10 '20 at 23:52

score 2 · Accepted Answer · answered Jun 11 '20 at 20:51

Well, like others said, it's probably not the preferred way to represent your data in tiles, but rather use geom_point. In that case, here's something that works:

ggplot(exa, aes(x,y,color=z)) +
  geom_point(size=3) +
  scale_color_gradientn(colors = pal)

If you still want to use tiles, as others mentioned, you cannot see the tiles because theya are just too small. You can make them larger to see by specifying width= and height=. Since your scales for x and y axis are different, you can't specify the same number if you want square-ish tiles. For that, you can use a bit 'o math to do that for you. Here's something that works:

w= 0.02 * (max(exa$x)-min(exa$x))
h= 0.02 * (max(exa$y)-min(exa$y))

ggplot(exa, aes(x,y,fill=z)) +
  geom_tile(width=w, height=h) +
  scale_fill_gradientn(colors = pal)

BTW - the tiles there are still not square due to the aspect ratio of the plot.

geom_tile in ggplot2 returning blank plot

1 Answers1