How to expand color palette with ggplot and RColorBrewer

ggplot_mtcars_barplot.R

library(ggplot2)
data(mtcars)
 
ggplot(mtcars) +
  geom_bar(aes(factor(cyl), fill=factor(cyl)))

ggplot_mtcars_fill_brewer.R

ggplot(mtcars) +
  geom_bar(aes(factor(cyl), fill=factor(cyl))) +
  scale_fill_brewer()

ggplot_mtcars_fill_brewer_palette.R

ggplot(mtcars) +
  geom_bar(aes(factor(cyl), fill=factor(cyl))) +
  scale_fill_brewer(palette="Set1")

ggplot_mtcars_hist.R

ggplot(mtcars) +
  geom_histogram(aes(factor(cyl), fill=factor(cyl)), stat="count")

ggplot_mtcars_hp.R

ggplot(mtcars) + 
  geom_bar(aes(factor(hp), fill=factor(hp))) +
  scale_fill_brewer(palette="Set2")

ggplot_mtcars_hp_22.R

colourCount = length(unique(mtcars$hp))
getPalette = colorRampPalette(brewer.pal(9, "Set1"))
 
ggplot(mtcars) + 
  geom_bar(aes(factor(hp)), fill=getPalette(colourCount)) + 
  theme(legend.position="right")

ggplot_mtcars_hp_aes.R

ggplot(mtcars) + 
  geom_bar(aes(factor(hp), fill=factor(hp))) + 
  scale_fill_manual(values = getPalette(colourCount))

ggplot_mtcars_legend_example.R

ggplot(mtcars) + 
  geom_bar(aes(factor(hp), fill=factor(hp))) + 
  scale_fill_manual(values = colorRampPalette(brewer.pal(8, "Accent"))(colourCount),
                    guide = guide_legend(nrow=2)) +
  theme(legend.position="bottom")

ggplot_mtcars_legend_position.R

ggplot(mtcars) + 
  geom_bar(aes(factor(hp), fill=factor(hp))) + 
  scale_fill_manual(values = getPalette(colourCount),
                    guide = guide_legend(nrow=2)) +
  theme(legend.position="bottom")

ggplot_mtcars_solarized.R

library(ggthemes)
library(scales)

show_col(solarized_pal()(8))

ggplot(mtcars) +
  geom_bar(aes(factor(hp), fill=factor(hp))) +
  scale_fill_manual(values = colorRampPalette(solarized_pal()(8))(colourCount),
                    guide = guide_legend(nrow=2)) +
  theme(legend.position="bottom")

rcolorbrewer_palettes.R

library(RColorBrewer)

display.brewer.all()

display.brewer.pal(9, "Set1")