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r programming language linkedin assessment answers

1. Review line 1 below. What does the statement in line 2 return?

1 mylist<-list(1,2,"C",4,5)
2 unlist(mylist)

  • [1] 1 2 C 4 5
  • [1] “1” “2” “C” “4” “5”
  • “C”
  • [1] 1 2 4 5

2. Which strings could be returned by the function ls (pat="^V" )?

  • VisitPCA, VarX
  • Xvar, Yvar
  • ANOVAData, anovadata
  • VisitPCA, varx

3. Which option setting can cause difficulty if you want to add to a variable's possible values after you have designed an object's initial data structure?

  • options (max.print=5)
  • options (stringsAsFactors=TRUE)
  • options (colnames (x) <- NULL)
  • options (continue=”…”)

4. Which choice returns [11 "2019-09-28"?

5. In the image below, the data frame on lines 1 through 4 is named StDf. StDf contains no factors. Why does the statement on line 6 return "character" while the statement on line 7 returns "data.frame"?

  • By specifying the final row, 3, and no column specified, StDf[3,] calls for the complete structure.
  • Columns in a data frame are vectors generally containing a single type of data. Rows in a data frame are lists, but they belong to a structure that has multiple rows: the data frame.
  • Each value in the first column is a character value, but the values in the third row include both character and numeric values.
  • Each value in the first row is a character value, but the values in the third column include both character and numeric values.

6. The variable potus is a character vector, as shown in line 1 below. Which statement returns the results shown?

  • potus[1:2 4]
  • potus[-3]
  • potus[1,2,4]
  • potus[-“GW Bush” ]

7. Review line 1. What does the statement on line 3 return?

1 mtrx <- matrix(1:6, 3, 2)
3 mtrx[, -1]

8. What does the function power. anova. test return?

  • the probability of making a Type Il error
  • the probability of not making a Type Il error
  • the probability of not making a Type I error
  • the probability of making a Type I error

9. How do you get documentation of an installed and loaded R package named dplyr and packages with dplyr as an alias?

  • ? dplyr
  • Press the F1 key.
  • help(dplyr)
  • ?? dplyr

10. × is a vector of type integer, as shown in line 1 below. What is the type of the result returned by the statement > median (x)?

1 x <- c (12L, 6L,10L, 8L,15L,14L,19L,18L, 23L, 59L)

  • integer
  • single
  • double
  • numeric

11. You have data on the degree of approval for a ballot measure from Democrats, Republicans, and Independents. To test the statistical significance of the difference between any of the party means, which R function should you use?

  • t.test {stats}
  • power.t.test {stats}
  • TestA {DescTools}
  • anova.lm {stats}

12. d. pizza is a data frame. Its column named temperature contains only numbers. If you extract temperature using the [1 accessors, its class defaults to numeric. How can you access temperature so that it retains the class of data. frame?

> class( d.pizzal[ , "temperature" ] )
> "numeric"

  • class([ , “temperature”, drop=F ] )
  • class($temperature )
  • class([ , “temperature”] )
  • class( , “temperature”) )

13. Why does sum(! ) return the number of rows with valid, non-NA values in the column named week?

  • ! (pizza$week) returns a vector of TRUE/FALSE values, in which TRUE is treated as a 0 and FALSE as a 1.
  • ! (pizza$week) counts the number of NA values in the column.
  • The exclamation point in ! (pizza$week) reverses the meaning of the test it precedes.
  • ! (pizza$week) counts the number of non-missing values in the column.

14. How do you obtain the row numbers in a data frame named pizza for which the value of pizza$delivery min is greater than or equal to 30?

15. ournames is a character vector. What values does the statement below return to Cpeople?

Cpeople <- ournames %in% grep("^C", ournames, value = TRUE)

  • TRUE or FALSE, depending on whether any character in ournames is C
  • records where the first character is a C
  • TRUE and FALSE values, depending on whether the first character in an ournames record is C
  • any record with a value containing a C

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