题目
题目

COMM_V 205 101 102 103 2025W1 Exam B2 (R) 2025W1 Final - Requires Respondus LockDown Browser

多项填空题

Suppose you have given a subset of our North American Stock Market dataset in a data frame called compdf. There are all the 50 columns. Similar to our North American Stock Market dataset, gvkey and fyear combination uniquely identifies each observation in compdf. If you execute length(unique(compdf$loc)), you are returned 7. If you execute compdf %>% group_by(gvkey) %>% summarise(count = n()) , all the values under count column are 20.  Suppose you executed the following code successfully. df1 <- compdf %>% group_by(loc, fyear) %>% summarise(stat1 = mean(at, na.rm = TRUE), stat2 = max(stat1))   df1 should have [Fill in the blank] rows and 4 columns. If the information provided in the question is not sufficient, please type "not enough information". 

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思路分析
The task asks for filling two blanks in a pipeline that groups by loc and fyear, then computes two summaries per group. First, understand what df1 will contain: after grouping by loc and fyear, you produce one row per distinct pair of (loc, fyear) across the entire compdf dataset, since summarise reduces each group to a single row. Second, examine the structure of compdf as described: there are 7 distinct loc values (length(unique(compdf$loc)) = 7). You are told that within the data, every gvkey has 20 observations (the gr......Login to view full explanation

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