r - ggplot heatmap failing to fill tiles -

this (minimal, self-contained) example broken:

require(ggplot2)   min_input = c(1, 1, 1, 2, 2, 2, 4, 4, 4) input_range = c(4, 470, 1003, 4, 470, 1003, 4, 470, 1003) density = c(     1.875000e-01,     5.598958e-04,     0.000000e+00,     1.250000e-02,     3.841146e-04,     0.000000e+00,     1.250000e-02,     1.855469e-04,     0.000000e+00)         df = data.frame(min_input, input_range, density)  pdf(file='problemspace.pdf') ggplot(df, aes(x=min_input, y=input_range, fill=density)) +     geom_tile() dev.off() 

producing:

why there big gaps?

there gaps because don't have data of tiles. if want try fill them in, option interpolate (assuming don't have access additional data). in theory, geom_raster() (a close relative of geom_tile()) supports interpolation. however, according this github issue, feature not functional.

as workaround, however, can use qplot, wrapper around ggplot:

qplot(min_input, input_range, data=df, geom="raster", fill=density, interpolate=true) 

if there space between points have data for, still end blank spaces in graph, extend range can estimate values for.

edit:

based on example posted, output

as can see, there vertical band of white running through middle, due lack of data points between 2 , 4.