使用dplyr选择前n组，然后绘制其他变量
使用dplyr选择前n组，然后绘制其他变量
提问于 2019-01-19 04:09:11
我有一个数据集，我试图通过计算一个类别来只选择前n个，然后使用数据集中的其他变量进行绘图--基本上是前n个类别的一级聚合，但需要返回到完整的数据才能在ggplot中绘图。
因此，在下面的问题中，我想要两个最常见的计数，然后绘制并按year计数对它们进行facetwrap。
ap <-
tribble(
~year, ~examName,
2014, "Statistics",
2015, "Statistics",
2016, "Statistics",
2016, "Statistics",
2016, "Statistics",
2016, "Statistics",
2017, "Statistics",
2017, "Statistics",
2017, "Statistics",
2017, "Statistics",
2017, "Statistics",
2013, "Macroeconomics",
2013, "Macroeconomics",
2014, "Macroeconomics",
2015, "Macroeconomics",
2016, "Macroeconomics",
2016, "Macroeconomics",
2016, "Macroeconomics",
2016, "Macroeconomics",
2016, "Macroeconomics",
2017, "Macroeconomics",
2017, "Macroeconomics",
2017, "Macroeconomics",
2017, "Macroeconomics",
2017, "Macroeconomics",
2017, "Macroeconomics",
2013, "Calculus",
2014, "Calculus",
2015, "Calculus",
2016, "Calculus",
2017, "Calculus",
2017, "Psychology",
2017, "Psychology",
2017, "Psychology",
2017, "Psychology",
2017, "Psychology",
2018, "Psychology",
2018, "Psychology")
ap_top <- ap %>%
count(examName, sort = TRUE) %>%
head(2) %>%
inner_join(ap, by = "examName") %>%
select(-n)
ap_top %>%
count(examName, year) %>%
ggplot(aes(x = year, y = n, group = examName)) +
geom_line() +
facet_wrap(~ examName)我的想法是获取前n，然后在原始数据集上执行inner_join。然后使用它进行绘图；本质上是使用内部连接作为过滤器。
我知道有一种更好的方法可以做到这一点，我希望有一个更优雅的解决方案！我在认真地听呢!给出了示例数据集(对不起，它太长了)。
回答 2
Stack Overflow用户
回答已采纳
发布于 2019-01-19 04:21:18
您不需要inner_join()，我只需要在单独的语句中确定前两个考试，然后对它们进行过滤。
top_exams <- count(ap, examName) %>%
top_n(2, n) %>% pull(examName)
ap %>%
filter(examName %in% top_exams) %>%
count(year, examName) %>%
ggplot(aes(x = year, y = n, group = examName)) +
geom_line() +
facet_wrap(~ examName)Stack Overflow用户
发布于 2019-01-19 04:43:11
另一种可能性是：
ap %>%
group_by(examName) %>%
mutate(temp = n()) %>%
ungroup() %>%
mutate(temp = dense_rank(desc(temp))) %>%
filter(temp %in% c(1,2)) %>%
select(-temp) %>%
count(year, examName) %>%
ggplot(aes(x = year, y = n, group = examName)) +
geom_line() +
facet_wrap(~ examName)它对每个"examName“的案例进行计数，并对计数进行排序。然后，它过滤具有最大计数和第二大计数的案例。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/54260789
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