r - Categorical axis to Continuous ggplot -

i trying create heat map, each tile month. if use dates data date type, lines on image not acceptable.

so solution has been to treat date factor

the problem axis not presentable. there way merge 2 plots x axis first plot, tiles second plot?

ggplot(df, aes(x    = factor(var2),            y    = factor(desc(var1)),            fill = value)) + 

as reproducible example:

df <- read.table("","var1","var2","value","col"                  "1",2001-01-31,2001-01-31,-0.0118511587908436,"blue"                  "2",2001-02-28,2001-01-31,0,"white"                  "3",2001-03-30,2001-01-31,0,"white"                  "4",2001-04-30,2001-01-31,0,"white"                  "5",2001-05-31,2001-01-31,0,"white"                  "6",2001-06-29,2001-01-31,0,"white")  ggplot(dff, aes(x   = factor(var2),            y    = factor(desc(var1)),            fill = col)) +   geom_tile() +   scale_x_discrete(breaks=pretty(p$var2))  

output example

use dates manually remove grid. can adding + theme(panel.grid = element_blank()) plot.