How to control stripe transparency using ggforestplot/geom_stripes?

Question

I was hoping to have some help in modifying the stripe transparency/shading color in the ggforestplot package. Please see the image below ("lighten" indicates the stripes I need to lighten). What is the best way of modifying the following code to do that?

Thank you so much for any pointers!

# Load and attach the packages
library(ggforestplot)
library (ggplot2)
library(tidyverse)

#  Reproducible dataset
df <- ggforestplot::df_linear_associations %>% filter(  trait == "BMI", dplyr::row_number() <= 30)

# Draw a forestplot 
ggforestplot::forestplot(
  df = df,
  name = name,
  estimate = beta,
  se = se)+ 
geom_point(shape = 15, size = 5) +

geom_stripes( odd ="#00000000",  even = "#00000000") +

theme(legend.position="none",
     panel.background = element_rect(fill = "transparent",colour = NA),
        plot.background = element_rect(fill = "transparent",colour = NA))

Answer 1

The issue is that ggforestplot::forestplot already adds a geom_stripes layer with hard-coded default values for odd and even. Adding another geom_stripes will have no effect on this underlying stripes layer and will simply result in overplotting of the points, vertical lines, ... . To adjust the transparency you could (and TBMK need to) hack the internals:

# Load and attach the packages
library(ggforestplot)
library(ggplot2)
library(tidyverse)

#  Reproducible dataset
df <- ggforestplot::df_linear_associations %>% filter(  trait == "BMI", dplyr::row_number() <= 30)

# Draw a forestplot 
p <- ggforestplot::forestplot(
  df = df,
  name = name,
  estimate = beta,
  se = se) + 
  geom_point(shape = 15, size = 5) +
  theme(legend.position="none",
        panel.background = element_rect(fill = "transparent"))

p$layers[[1]]$aes_params$odd <- "#00000000"

p