rcpp_forloop.R

# Load the Rcpp library (assuming you've already loaded it earlier)
library(Rcpp)
library(showtext)
library(ggplot2)
library(ggforce)
library(ggfx)

## Loading Google fonts (https://fonts.google.com/)
font_add_google("Exo 2", "Exo")
showtext_auto()


# The C++ code
cppFunction('
DataFrame generate_lines_within_circle(double center_x, double center_y, 
                                       double radius, int num_lines) {
  // RNGScope is a helper class that sets up the R random number generator
  RNGScope scope;

  NumericVector start_angles = runif(num_lines, 0, 2 * M_PI);
  NumericVector end_angles = start_angles + runif(num_lines, 0, 2 * M_PI);

  NumericVector start_x(num_lines);
  NumericVector start_y(num_lines);
  NumericVector end_x(num_lines);
  NumericVector end_y(num_lines);

  for(int i = 0; i < num_lines; ++i) {
      start_x[i] = center_x + radius * cos(start_angles[i]);
      start_y[i] = center_y + radius * sin(start_angles[i]);
      end_x[i] = center_x + radius * cos(end_angles[i]);
      end_y[i] = center_y + radius * sin(end_angles[i]);
  }

  return DataFrame::create(Named("start_x") = start_x,
                           Named("start_y") = start_y,
                           Named("end_x") = end_x,
                           Named("end_y") = end_y);
}
')

# Circle parameters
center_x <- 0.5
center_y <- 0.5
radius <- 0.4

# Number of lines to generate within the circle
num_lines <- 1000

# Generate random lines within the circle using the C++ function
lines_within_circle <- generate_lines_within_circle(center_x, center_y, radius, num_lines)
lines_within_circle


ggplot() +
  with_outer_glow(geom_circle(aes(x0 = center_x, y0 = center_y, r = radius), fill = NA, color = "#333333"),colour="white",sigma=,expand=0.5) +
  purrr::pmap(
    .l = lines_within_circle,
    .f = function(start_x, start_y, end_x, end_y) {
      geom_segment(
        aes(x = start_x, y = start_y, xend = end_x, yend = end_y),
        color = 'gray',
        linewidth = 0.1
      )
    }
  ) +
  coord_fixed() +
  labs(title="Moon") +
  theme_void() +
  theme(legend.position = "none", 
        plot.title=element_text(family="Exo", size=28, hjust=0.5, color="#8d96a3"),
        panel.background = element_rect(fill = "#333333", color=NA),
        plot.background = element_rect(fill = "#333333", color=NA), 
        panel.grid = element_blank(),
        panel.grid.major = element_blank(),
        panel.grid.minor = element_blank())