How do I keep all the legends in ggplot - r

Question

How do I keep all the legends in plot?
Below is an example of scatter plot. It prints only if x > 0.5. But I want to show all the legends.
library(tidyverse)
for (iter in 1:5)
{
# generate 5 random points
tbl <- tibble(x = runif(5),
y = runif(5),
class = c("A", "B", "C", "D", "E"))
# print if x > 0.5
p <- ggplot(data = tbl %>% filter(x > 0.5),
aes(x = x,
y = y,
color = class)) +
geom_point(size = 5) +
scale_fill_manual(labels = c("A", "B", "C", "D", "E"),
values = c("Grey", "Red", "Green", "Blue", "Yellow"),
drop = FALSE) +
theme_bw() +
theme(aspect.ratio = 1) +
xlim(0, 1) +
ylim(0, 1)
ggsave(p,
filename = paste0(iter, ".png"))
}

Answer 1

You can do it if:
you set the class variable to factor
use scale_colour_manual instead of scale_fill_manual. If you want to use the default colour from the ggplot palette you can use scale_colour_descrete, as in my code.
library(tidyverse)
set.seed(1) # for reproducibility
plots <- lapply(1:5, function(iter){
# generate 5 random points
tbl <- tibble(x = runif(5),
y = runif(5),
class = factor(c("A", "B", "C", "D", "E")))
# print if x > 0.5
p <- ggplot(data = tbl %>% filter(x > 0.5),
aes(x = x,
y = y,
color = class)) +
geom_point(size = 5) +
scale_colour_discrete(drop = FALSE) +
theme_bw() +
theme(aspect.ratio = 1) +
xlim(0, 1) +
ylim(0, 1)
ggsave(p, filename = paste0(iter, ".png"))
p
})
# visualize them all together
cowplot::plot_grid(plotlist = plots)
PS: I've used lapply instead of a for loop, usually it is more appreciated by R users when possible.

Answer 2

Instead of filtering out the data you can change the values to NA:
library(tidyverse)
for (iter in 1:5)
{
# generate 5 random points
tbl <- tibble(x = runif(5),
y = runif(5),
class = c("A", "B", "C", "D", "E"))
# print if x > 0.5
p <- ggplot(data = tbl %>% mutate(y = if_else(x > 0.5, y, NA_real_)),
aes(x = x,
y = y,
color = class)) +
geom_point(size = 5) +
scale_fill_manual(labels = c("A", "B", "C", "D", "E"),
values = c("Grey", "Red", "Green", "Blue", "Yellow"),
drop = FALSE) +
theme_bw() +
theme(aspect.ratio = 1) +
xlim(0, 1) +
ylim(0, 1)
ggsave(p,
filename = paste0(iter, ".png"))
}