How to change a density curve without changing the legend in ggplot2?

December 17, 2021

I want to change the color of the density curve but when I change it, the border of the boxes from the legend changes too.

Original plot:

When I change the color of the density curve:

Also, if I add lwd=1.2 from the density curve, the legend changes too.

Does anyone know how to fix it?
(I want to change the line width and the colour of the density curve, but I don’t want to change how the legend looks).

This is the code:

val1 <- c(2.1490626,3.7928443,2.2035281,1.5927854,3.1399245,2.3967338,3.7915825,4.6691277,3.0727319,2.9230937,2.6239759,3.7664386,4.0160378,1.2500835,4.7648343,0.0000000,5.6740227,2.7510256,3.0709322,2.7998003,4.0809085,2.5178086,5.9713330,2.7779843,3.6724801,4.2648527,3.6841084,2.5597235,3.8477471,2.6587736,2.2742209,4.5862788,6.1989269,4.1167091,3.1769325,4.2404515,5.3627032,4.1576810,4.3387921,1.4024381,0.0000000,4.3999099,3.4381837,4.8269218,2.6308474,5.3481382,4.9549753,4.5389650,1.3002293,2.8648220,2.4015338,2.0962332,2.6774765,3.0581759,2.5786137,5.0539080,3.8545796,4.3429043,4.2233248,2.0434363,4.5980727)
val2 <- c(3.7691229,3.6478055,0.5435826,1.9665861,3.0802654,1.2248374,1.7311236,2.2492826,2.2365337,1.5726119,2.0147144,2.3550348,1.9527204,3.3689502,1.7847986,3.5901329,1.6833872,3.4240479,1.8372175,0.0000000,2.5701453,3.6551315,4.0327091,3.8781182)

df1 <- data.frame(value = val1)   
df2 <- data.frame(value = val2)   

data <- bind_rows(lst(df1, df2), .id = 'id')

data %>% 
ggplot(aes(value)) +
  geom_histogram(aes(y=..density.., fill = id), bins=10, col="black", alpha=0.4) +
  geom_density(lwd = 1.2,
               colour = "red") +
  facet_grid(id ~ .) + 
  scale_x_continuous(breaks=pretty(data$value, n=10)) +
  ggtitle("My histogram....") +
  guides(fill=guide_legend(title="My legend...")) +
  theme(strip.text.x = element_blank(),strip.text.y = element_blank())

Thanks very much in advance!

Regards

>Solution :

Add show.legend = FALSE to geom_density()

library(ggplot2)
library(dplyr)

data %>% 
  ggplot(aes(value)) +
  geom_histogram(aes(y=..density.., fill = id), bins=10, col="black", alpha=0.4) +
  geom_density(lwd = 1.2, colour = "red", show.legend = FALSE) +
  facet_grid(id ~ .) + 
  scale_x_continuous(breaks=pretty(data$value, n=10)) +
  ggtitle("My histogram....") +
  guides(fill = guide_legend(title="My legend...")) +
  theme(strip.text.x = element_blank(),strip.text.y = element_blank())