用条件总结计数

Question

我有一个数据框，其中包含许多年内一堆物种的样方计数，但有时它们不是计数，而是标记为“p”，表示“现在”。我想对它们进行平均，同时在平均中将这些 p 计算为 NA，但还要跟踪每个 species/year 中 p 的数量，所以我的问题是，有没有办法使用 summarize(count) 来计算 P 的出现次数？

最小示例：

df <- data.frame(
  # years
  year = rep(1990:1992, each=3),
  # character vector of counts and p's
  count = c("p","p","2","1","5","4","7","p","4")
) %>%
  # numeric column of counts and NAs where P's should be
  mutate(count_numeric = as.numeric(count))


# summarize dataset
df %>%
  group_by(year) %>%
  summarize(number_quadrats = n(), # find total number of rows
            average_count = mean(count_numeric, na.rm=T)) # find average value

但我想在摘要中添加另一行，只计算每组中 P 的数量。像这样：

df %>%
  group_by(year) %>%
  summarize(number_quadrats = n(), # find total number of rows
            average_count = mean(count_numeric, na.rm=T),# find average value
            number_p = n(count == "p"))

但这不起作用。

感谢任何建议。

谢谢！

Answer 1

只需更改最后一行：

df %>%
group_by(year) %>%
summarize(number_quadrats = n(), # find total number of rows
          average_count = mean(count_numeric, na.rm=T),# find average value
          number_p = sum(count == "p"))

通过对布尔向量求和，您实际上是在计算满足条件的次数。

Answer 2

像这样！

df %>%
  group_by(year) %>%
  summarize(N = n(), number_quadrats = sum(count == 'p'),
            average_count = mean(count_numeric, na.rm=T))

  year     N number_quadrats average_count
  <int> <int>           <int>         <dbl>
1  1990     3               2          2   
2  1991     3               0          3.33
3  1992     3               1          5.5

用条件总结计数

summarize count with a condition

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