How to change the scale color of the legend of raster ggplot2 R

Question

I want to expose my problem, in order to give me some ways forward. My goal is to display a card with my full raster from this program :

library(raster) ; library(rgdal) ; library(sp);library(rgeos);library(ggplot2)

alti=raster("raster.tif")

hdf <- rasterToPoints(alti)

hdf <- data.frame(hdf)

colnames(hdf) <- c("Long","Lat","Altitude")

ggplot()+
  layer(geom="raster",data=hdf,mapping=aes(Long,Lat,fill=Altitude))+
      # draw boundaries
  geom_path(color="black", linestyle=0.2)+
    scale_fill_gradientn(name="A",colours=c("red","blue","green","grey","yellow","orange","black"), breaks=c(0,100,200,500,750,1000,2000))

At the end, I can not to adjust colors of my legend with ranges of value I have proposed.

I want to have this legend :

  red : 0-100.
  blue : 100-200.
  green : 200-500.
  grey : 500-750.
  yellow : 750-1000.
  orange : 1000-2000.
  black : upper 2000.

example: normally for the range [1000-2000] it's orange , but in my result on the legend there are 3 colors grey , yellow and orange . I want the limits of my intervals should correspond to the value limits of the colors in the legend.

Answer 1

If you create a factor variable from your Altitude column and use scale_fill_manual() , you can get it to work properly. It will also create nice labels for your legend automatically:

library(raster) ; library(rgdal) ; library(sp);library(rgeos);library(ggplot2)

alti=raster("raster.tif")

hdf <- rasterToPoints(alti)

hdf <- data.frame(hdf)

colnames(hdf) <- c("Long","Lat","Altitude")

tmp <- hdf$Altitude
hdf$Altitude <- ifelse(tmp <= 100, "0-100", hdf$Altitude)
hdf$Altitude <- ifelse(tmp > 100 & tmp <= 200, "100-200", hdf$Altitude)
hdf$Altitude <- ifelse(tmp > 200 & tmp <= 500, "200-500", hdf$Altitude)
hdf$Altitude <- ifelse(tmp > 500 & tmp <= 750, "500-750", hdf$Altitude)
hdf$Altitude <- ifelse(tmp > 750 & tmp <= 1000, "750-1000", hdf$Altitude)
hdf$Altitude <- ifelse(tmp > 1000 & tmp <= 2000, "1000-2000", hdf$Altitude)
hdf$Altitude <- ifelse(tmp > 2000, "Upper 2000", hdf$Altitude)
hdf$Altitude <- factor(hdf$Altitude)

g <- ggplot()+
  layer(geom="raster",data=hdf,mapping=aes(Long,Lat,fill=Altitude))+
      # draw boundaries
  geom_path(color="black", linestyle=0.2)+
    scale_fill_manual(values = c("red","blue","green","grey","yellow","orange","black"))