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Exercise

Customize readWorksheet

To get a clear overview about urbanpop.xlsx (view) without having to open up the Excel file, you can execute the following code:

my_book <- loadWorkbook("urbanpop.xlsx")
sheets <- getSheets(my_book)
all <- lapply(sheets, readWorksheet, object = my_book)
str(all)

Suppose we're only interested in urban population data of the years 1968, 1969 and 1970. The data for these years is in the columns 3, 4, and 5 of the second sheet. Only selecting these columns will leave us in the dark about the actual countries the figures belong to.

Instructions
100 XP
  • Extend the readWorksheet() command with the startCol and endCol arguments to only import the columns 3, 4, and 5 of the second sheet.
  • urbanpop_sel no longer contains information about the countries now. Can you write another readWorksheet() command that imports only the first column from the second sheet? Store the resulting data frame as countries.
  • Use cbind() to paste together countries and urbanpop_sel, in this order. Store the result as selection.
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