geom_tile heatmap with different high fill colours based on factor

ggplot2, heatmap, r

Solution

In general, ggplot2 does not permit multiple scales of a single type (i.e. multiple colour or fill scales), so I suspect that this isn't (easily) possible.

The best nearest approximation I can come up with is this:

df <- data.frame(expand.grid(1:5,1:5))
df$z <- runif(nrow(df))
df$grp <- rep(letters[1:2],length.out = nrow(df))

ggplot(df,aes(x = Var1,y = Var2,fill = factor(grp),alpha = z)) + 
    geom_tile() + 
    scale_fill_manual(values = c('red','blue'))

But it's going to be tough to get a sensible legend.

Problem

I'm interested in building a heatmap with `geom_tile` in ggplot2 that uses a different gradient high color based on a factor. The plot below creates the plot where the individual tiles are colored blue or red based on the `xy_type`, but there is no gradient. ``` ggplot() + geom_tile(data=mydata, aes(x=factor(myx), y=myy, fill=factor(xy_type))) + scale_fill_manual(values=c("blue", "red")) ``` The plot below does not use the `xy_type` factor to choose the color, but I get a single group gradient based on the `xy_avg_value`. ``` ggplot() + geom_tile(data=mydata, aes(x=factor(myx), y=myy, fill=xy_avg_value)) ``` Is there a technique to blend these two plots? I can use a `facet_grid(xy_type ~ .)` to create separate plots of this data, with the gradient. As this is ultimately going to be a map (x~y coordinates), I'd like to find a way to display the different gradient together in a single `geom_tile` map.

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