元旦特刊 | 2020年元旦夜演：用R玩烟花，用心写代码

欢乐过新年，烟花灿九天。

新年伊始，数据Seminar全体人员，祝大家新年快乐，事事如意！本期特刊，我们用R语言绘制出“烟花夜景图”，与大家一同欢度佳节！

烟花夜景

图：元旦·烟花夜景

R绘制手工烟花

烟花图由Thomas Lin Pedersen开发，主要通过R语言中的ggplot2和gganimate包绘制而成。利用color（）函数采样颜色，并控制blast（）函数从中心到外围创建片段，然后用ggplot2包绘出静态图形，辅以gganimate包输出动画效果。下面是上图烟花的基本绘图代码，供参考：

##制作烟花(Making Fireworks)
##加载包
library(ggplot2)
library(gganimate)

# Firework colours
colours <- c('lawngreen','gold','white','orchid','royalblue','yellow','orange')

# Produce data for a single blast
blast <- function(n, radius, x0, y0, time) {
  u <- runif(n, -1, 1)
  rho <- runif(n, 0, 2*pi)
  x <- radius * sqrt(1 - u^2) * cos(rho) + x0
  y <- radius * sqrt(1 - u^2) * sin(rho) + y0
  id <- sample(.Machine$integer.max, n + 1)
  data.frame(
    x = c(x0, rep(x0, n), x0, x),
    y = c(0, rep(y0, n), y0, y),
    id = rep(id, 2),
    time = c((time - y0) * runif(1), rep(time, n), time, time + radius + rnorm(n)),
    colour = c('white', rep(sample(colours, 1), n),
               'white', rep(sample(colours, 1), n)),
    stringsAsFactors = FALSE
  )
}

# Make 20 blasts
n <- round(rnorm(20, 30, 4))
radius <- round(n + sqrt(n))
x0 <- runif(20, -30, 30)
y0 <- runif(20, 40, 80)
time <- runif(20, max = 100)
fireworks <- Map(blast, n = n, radius = radius, x0 = x0, y0 = y0, time = time)
fireworks <- dplyr::bind_rows(fireworks)

# Make Fireworks
ggplot(fireworks) + 
  geom_path(aes(x = x, y = y, group = id, colour = colour)) + 
  scale_colour_identity()

ggplot(fireworks) + 
  geom_point(aes(x, y, colour = colour, group = id), size = 0.5, shape = 20) + 
  scale_colour_identity() + 
  coord_fixed(xlim = c(-55, 55), expand = FALSE, clip = 'off') +
  theme_void() + 
  theme(plot.background = element_rect(fill = 'black', colour = NA),
        panel.border = element_blank()) + 
  # Here comes the gganimate code
  transition_components(time, exit_length = 20) + 
  ease_aes(x = 'sine-out', y = 'sine-out') + 
  shadow_wake(0.05, size = 3, alpha = TRUE, wrap = FALSE,
              falloff = 'sine-in', exclude_phase = 'enter') + 
  exit_recolour(colour = 'black')

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烟花夜景调相

利用调相软件，我们还可以做出更加美观流畅的图形效果：

点击左下角阅读原文查看更多

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数据Seminar

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作者：简华（何年华）审阅：杨奇明、谈佳辉编辑：青酱

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