R: Hide geom_segment() if a certain condition is true? - r

Question

I use geom_segment() from ggplot2 package in R, where the data attribute is a vector with two elements. The segment is an arrow. I want to hide the segment if one of the elements of the data vector equals 0. Is there a way to only plot the segment if a certain condition is true?
If an example is needed to understand what I mean, please let me know. My current use case is quite complex and requires some preparation to be shown here.
EDIT: Here's my reduced but working example, taken from this post and extended a little bit. I want the arrows not to show up when exposure_time is 0.
# load necessary libraries
library(ggplot2)
library(sf)
# load csv data
photo_positions <- readr::read_csv("photos_hamburg2.csv") |>
sf::st_as_sf(coords=c('X', 'Y'))
# transform degrees to radians for orientation values
photo_positions[['orientation_rad']] = photo_positions[['orientation']] * pi / 180
# define a length_factor
length_factor <- .2
# test plot
ggplot(data = photo_positions) +
# extract coordinates
stat_sf_coordinates() +
# draw arrows with orientation and length from attributes
geom_segment(
stat = "sf_coordinates",
mapping = aes(
geometry = geometry,
x = after_stat(x),
y = after_stat(y),
xend = after_stat(x) + photo_positions[['exposure_time']] * length_factor * sin(photo_positions[['orientation_rad']]),
yend = after_stat(y) + photo_positions[['exposure_time']] * length_factor * cos(photo_positions[['orientation_rad']])
),
arrow = arrow(),
size = 2,
color = "turquoise"
) +
# draw circle markers
geom_sf(stat = "sf_coordinates", mapping = aes(geometry = geometry, x = after_stat(x), y = after_stat(y)), size = 4, shape = 21, fill = "white") +
# axis labels
xlab("Longitude") + ylab("Latitude") +
#map title
ggtitle("Photos in Hamburg")
Not very realistic, but hopefully showing what I want to achieve. In my real use case I work with wind speeds and wind directions for different locations, but it was too complicated to reduce it to a suitable example.
CSV data used:
X,Y,name,orientation,exposure_time
9.991293,53.55456,"Alster view 2",59,0.004
9.992967,53.550898,"Rathaus view 2",219,0.008
9.995563,53.556932,"Alster view 1",201,0
9.992591,53.551986,"Rathaus view 1",177,0
9.995724,53.552775,"Alster view 3",338,0.016
Screenshot of the result (including arrows to be hidden)

Answer 1

Here's the solution with photo_positions <- photo_positions[photo_positions$'exposure_time' > 0,] from Jon Spring's comment included, based on the same CSV data as provided with the question.
# load necessary libraries
library(ggplot2)
library(sf)
# load csv data
photo_positions <- readr::read_csv("photos_hamburg2.csv") |>
sf::st_as_sf(coords=c('X', 'Y'))
# remove rows with zero values for exposure time data
photo_positions <- photo_positions[photo_positions$'exposure_time' > 0,]
# transform degrees to radians for orientation values
photo_positions[['orientation_rad']] = photo_positions[['orientation']] * pi / 180
# define a length_factor
length_factor <- .2
# test plot
ggplot(data = photo_positions) +
# extract coordinates
stat_sf_coordinates() +
# draw arrows with orientation and length from attributes
geom_segment(
stat = "sf_coordinates",
mapping = aes(
geometry = geometry,
x = after_stat(x),
y = after_stat(y),
xend = after_stat(x) + photo_positions[['exposure_time']] * length_factor * sin(photo_positions[['orientation_rad']]),
yend = after_stat(y) + photo_positions[['exposure_time']] * length_factor * cos(photo_positions[['orientation_rad']])
),
arrow = arrow(),
size = 2,
color = "turquoise"
) +
# draw circle markers
geom_sf(stat = "sf_coordinates", mapping = aes(geometry = geometry, x = after_stat(x), y = after_stat(y)), size = 4, shape = 21, fill = "white") +
# axis labels
xlab("Longitude") + ylab("Latitude") +
#map title
ggtitle("Photos in Hamburg")