使用坐标随机采样网格

Question

我在一张图片上放置了一个编号网格(19 X 22)，我需要从418帧中随机选择250帧。有没有一种方法可以通过随机选择x和y坐标来实现这一点，而不需要任何重复的坐标？

谢谢

Example of grid over image (rows and columns are not labeled)

Answer 1

这里有一个快速而肮脏的方法，可以生成随机的X和Y值，而不需要在网格中重复。

library(tidyverse) # Gives us both %>% and filter_n

# Create a dataframe (technically a tibble) with one cell for each
# cell in your grid
combos <- expand.grid(x = seq(1, 19, 1), y = seq(1, 22, 1)) %>%
  tbl_df()

# Draw 250 random samples from the data without replacement
# If you post more information about the data you're using,
# I might be able to skip the creation of the combos data entirely
grid_sample <- sample_n(combos, size = 250, replace = FALSE)

如果您发布一个您想要采样的数据类型的代码示例，我也许能够简化。