ggplot2 geom_tile: how to have no spacing between lines when plotting non-continuous data

Question

I'm trying to do a levelplot using ggplot2 for a (meteorological) variable. The variable is measured continuously in time (my x-axis), but in non-continuous heights (y-axis) at every time step. The produced plot therefore shows data at the heights (y-coordinates) specified, but nothing in between. Here's an example:

library(ggplot2)
data <- runif(400, min=0, max=10)
index <- c(1:20)
heights <- c(1,2,3,4,5,7,9,12,15,19,23,28,33,39,45,52,59,67,75,83)
dat <-     as.data.frame(cbind(expand.grid(X=index,Y=heights),data))                        
ggplot(dat, aes(x=dat[,1], y=dat[,2],z=dat[,3])) +geom_tile(aes(fill=dat[,3]))

This produces the following plot:

Is there an easy way to fill the plot fully, i.e. make the lines in the upper part of the plot broader? Thank you!

Answer 1

OK one more solution.. you could interpolate using the approx function. Although maybe 2D kriging would be more appropriate for your application???

library(purrr)
dat2<- dat %>%
  split(.$X) %>%
  map_dfr(~ approx(.$Y, .$data, xout =1:83), .id = "X") 

ggplot(dat2, aes(x=as.integer(dat2$X), y=dat2$x, z=dat2$y)) +geom_tile(aes(fill=dat2$y))

That will give you :

Answer 2

You can use the height and width attributes in geom_tile, alternatively geom_rect

library(tidyverse)
data <- runif(400, min=0, max=10)
index <- c(1:20)
heights <- c(1,2,3,4,5,7,9,12,15,19,23,28,33,39,45,52,59,67,75,83)

dat <- crossing(index = index, heights = heights) %>% 
  mutate(
    Z = data,
    index0 = index - 1) %>% 
  left_join(data_frame(heights, heights0 = c(0, heights[-length(heights)])))    

ggplot(dat, aes(xmin = index0, xmax = index, ymin = heights0, ymax = heights, fill = Z)) +
  geom_rect()

This assumes that your heights are the top of each level and that they start at zero.