ggplots-in-for-loops-dont-work.R

library(ggplot2)

# expected plot gg_manual
manual_plots <- list()
manual_plots[[1]] <- ggplot(penguins, aes(bill_len, m[,1])) + 
    geom_point() +
    labs(title = "Column 1")
manual_plots[[2]] <- ggplot(penguins, aes(bill_len, m[,2])) + 
    geom_point() +
    labs(title = "Column 2")
manual_plots[[3]] <- ggplot(penguins, aes(bill_len, m[,3])) + 
    geom_point() +
    labs(title = "Column 3")
manual_plots[[4]] <- ggplot(penguins, aes(bill_len, m[,4])) + 
    geom_point() +
    labs(title = "Column 4")
gg_manual <- patchwork::wrap_plots(manual_plots)
gg_manual

# The problem: This for loop does not plot data as expected
all_plots <- list()
m <- as.matrix(penguins[,3:6])
for (i in 1:ncol(m)) {
  gg <- ggplot(penguins, aes(bill_len, m[,i])) + 
    geom_point() +
    labs(title = sprintf("Column %i", i))
  all_plots[[i]] <- gg
}
gg_for <- patchwork::wrap_plots(all_plots)
gg_for | gg_manual

# Solution 1: Prepare colnames and use .data
all_plots <- list()
m <- as.matrix(penguins[,3:6])
m_cols <- colnames(penguins[,3:6])
for (i in 1:ncol(m)) {  
  gg <- ggplot(m, aes(bill_len, .data[[m_cols[i]]])) + # show the column name as y axis text
    geom_point() +
    labs(title = sprintf("Column %i", i))
  all_plots[[i]] <- gg
}
prepare_for <- patchwork::wrap_plots(all_plots)
prepare_for | gg_manual

# Solution 2: ggplotGrob to evaluate the plot (Source https://bsky.app/profile/tjmahr.com/post/3ml26koql7k2n)
all_plots <- list()
m <- as.matrix(penguins[, 3:6])
for (i in 1:ncol(m)) {
  gg <- ggplot(penguins, aes(bill_len, m[, i])) + # show m[, i] as y axis text
    geom_point() +
    labs(title = sprintf("Column %i", i))
  all_plots[[i]] <- ggplotGrob(gg)
}
gggg_for <- patchwork::wrap_plots(all_plots)
gggg_for | gg_manual

# Solution 3: bang bang (Source: https://gist.github.com/JosiahParry/a013c715dc719abf075a0cd1193f5aed?permalink_comment_id=5808395#gistcomment-5808395)
all_plots <- list()
m <- as.matrix(penguins[,3:6])
m_cols <- colnames(penguins[,3:6])
for (i in 1:ncol(m)) {  
  gg <- ggplot(penguins, aes(bill_len, m[, i])) + # show m[, 1], m[, 2]...  as y axis text
    geom_point() +
    labs(title = sprintf("Column %i", i))
  all_plots[[i]] <- gg
}
bangbang_for <- patchwork::wrap_plots(all_plots)
bangbang_for | gg_manual