Factoextra: How to change color of the average silhouette width in the fviz_silhouette function?

Question

I'm very curious about the ways to override the color value of the default red dashed line for average silhouette width in the fviz_silhouette function. Just peeked the fviz_silhouette code, and it puzzling me, why the author fixed line color parameter? (Listing from the function source code.)

p <- ggplot(df, mapping) + geom_bar(stat = "identity") + labs(y = "Silhouette width Si", x = "", title = paste0("Clusters silhouette plot ", 
            "\n Average silhouette width: ", round(mean(df$sil_width), 
                2))) + ggplot2::ylim(c(NA, 1)) + geom_hline(yintercept = mean(df$sil_width), 
        linetype = "dashed", color = "red")
    p <- ggpubr::ggpar(p, ...)

And the result with palette = "grey" and + theme_bw(), still preserves red dashed line, as in the image bellow.

Answer 1

You can edit the color via

p$layers[[2]]$aes_params$colour <- "black" # or whatever color you like

To demonstrate first make a plot (with the default red color line):

library(factoextra)
library(cluster)
data("iris")

iris.scaled <- scale(iris[, -5])

km.res <- kmeans(iris.scaled, 3, nstart = 2)

sil <- silhouette(km.res$cluster, dist(iris.scaled))
p <- fviz_silhouette(sil)
p

Now change the color to black:

p$layers[[2]]$aes_params$colour <- "black"
p