为何无法修改gganimate动画的帧数nframes？已解决

问题描述 #

使用gganimate制作动画，未指定nframes参数时渲染正常，但设置nframes = 300后触发以下错误：

nframes and fps adjusted to match transition
Error parsing framerate 8,4.                            
Error: Rendering with ffmpeg failed

重现代码 #

创建gganim对象的代码：

options(scipen = 999, OutDec  =  ",")

MonthlyAveragePrecipitationMap = ggplot(MonthlyAverageExtremePrecipitation) + 
  geom_path(data = map_data("world","Germany"),
            aes(x = long, y = lat, group = group)) +
  coord_fixed(xlim = c(6,15),
              ylim = c(47,55)) + 
  geom_point(aes(x=lon, y=lat, 
                 colour = ShareOfExtremePrecipitationEvents,
                 group = MonthOfYear),
             size = 3) + 
  scale_color_gradient(low="blue", high="yellow") + 
  xlab("Longitude (degree)") +
  ylab("Latitude (degree)") + 
  theme_bw() +
  transition_manual(frames = MonthOfYear) + 
  labs(title = '{unique(MonthlyAverageExtremePrecipitation$MonthOfYear)[as.integer(frame)]}', 
       color = paste0("Share of Extreme Precipitation Events \namong all Precipitation Events")) 

调用渲染的代码：

animate(MonthlyAveragePrecipitationMap,
        nframes = 300,
        renderer =
          ffmpeg_renderer(
            format = "auto",
            ffmpeg = NULL,
            options = list(pix_fmt = "yuv420p")))

问题原因 #

全局设置options(OutDec = ",")将系统默认的小数分隔符从英文点.替换为逗号,，gganimate在计算并传递帧率给ffmpeg时，会使用当前的小数分隔符格式化数值，而ffmpeg仅支持英文点作为小数分隔符，因此无法解析8,4这类格式的帧率值，导致渲染失败。

解决方法 #

避免全局修改小数分隔符，改为在需要显示逗号分隔小数的局部场景中单独设置：

1. 移除全局的OutDec = ","设置，保留其他必要的全局配置
2. 通过坐标轴的scale_*函数，指定标签的小数格式为逗号分隔

修改后的代码示例：

options(scipen = 999) # 仅保留科学计数法相关设置

MonthlyAveragePrecipitationMap = ggplot(MonthlyAverageExtremePrecipitation) + 
  geom_path(data = map_data("world","Germany"),
            aes(x = long, y = lat, group = group)) +
  coord_fixed(xlim = c(6,15),
              ylim = c(47,55)) + 
  geom_point(aes(x=lon, y=lat, 
                 colour = ShareOfExtremePrecipitationEvents,
                 group = MonthOfYear),
             size = 3) + 
  scale_color_gradient(low="blue", high="yellow") + 
  xlab("Longitude (degree)") +
  ylab("Latitude (degree)") + 
  # 局部设置坐标轴标签的小数分隔符为逗号
  scale_x_continuous(labels = ~format(.x, decimal.mark = ",")) +
  scale_y_continuous(labels = ~format(.x, decimal.mark = ",")) +
  theme_bw() +
  transition_manual(frames = MonthOfYear) + 
  labs(title = '{unique(MonthlyAverageExtremePrecipitation$MonthOfYear)[as.integer(frame)]}', 
       color = paste0("Share of Extreme Precipitation Events \namong all Precipitation Events")) 

这样既满足了数据显示时使用逗号作为小数分隔符的需求，又不会干扰gganimate与ffmpeg之间的数值传递，渲染即可正常进行。

内容的提问来源于stack exchange，提问作者RibbitRibbit