题目
题目

COMM_V 205 101 102 103 2025W1 R Review Quiz

多重下拉选择题

df_c<- student %>%   group_by(sid, year) %>%   summarise(min_grade = min(grade), ave_min_grade = mean(min_grade)) df_d<- student %>%   group_by(sid, year) %>%   summarise(min_grade = min(grade)) %>%   summarise(ave_min_grade = mean(min_grade))   Number of rows in df_c is different from that in df_d. There are 4 columns in df_c while there are 2 columns in df_d.  

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标准答案
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思路分析
Let’s walk through what the two pipelines are doing and what the resulting shapes look like step by step. First, inspect df_c: df_c <- student %>% group_by(sid, year) %>% summarise(min_grade = min(grade), ave_min_grade = mean(min_grade)). After grouping by sid and year, summarise creates one row per (sid, year) group and keeps the grouping keys in the output. The columns present are the grouping variables sid an......Login to view full explanation

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