R Online Test

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About the test

The R online test assesses knowledge of programming in the R language through a series of live coding tasks that focus on data analysis.

The assessment includes work-sample tasks such as:

  • Generating statistical reports.
  • Working with Vectors and DataFrames.
  • Cleaning data to avoid incorrect records.

A good R developer needs a solid understanding of the R programming language and the ability to take advantage of its rich set of built-in functions to support statistical and data analysis.

Sample public questions

15 min

A company stores login data and passwords in two different containers:

  • A DataFrame with the columns: id, name, and verified.
  • A matrix where each row contains, in order: id and password.

The first column of any row in the matrix corresponds to the id column in the DataFrame. Elements on the same row/index in both the DataFrame and the matrix have the same id.

Implement the function loginTable that accepts these two containers and returns a new DataFrame that contains the following columns:

  • The id column from the idNameVerified DataFrame.
  • The name column from the idNameVerified DataFrame.
  • A new column, called password that contains the password from the idPassword matrix.

For example, the following code snippet:

idNameVerified = data.frame(id = c(1, 2), 
    name = c("JohnDoe", "AnnFranklin"),
    verified = c(TRUE, FALSE))
idPassword = matrix(c(1, 2, 987340123, 187031122),


Should print:

  id        name  password
1  1     JohnDoe 987340123
2  2 AnnFranklin 187031122
10 min

Implement the function findRoots to find the roots of the quadratic equation: ax2 + bx + c = 0. The function should return a vector containing roots in any order. If the equation has only one solution, the function should return that solution as both elements of the vector. The equation will always have at least one solution.

The roots of the quadratic equation can be found with the following formula: A quadratic equation.

For example, findRoots(2, 10, 8) should return a vector containing (-1, -4) or (-4, -1) as the roots of the equation 2x2 + 10x + 8 = 0 are -1 and -4.

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5 more premium R questions

Recruitment Analytics, Median Height, Grocery Stores, Class Grades, Vectors.

Skills and topics tested

  • R
  • Vector
  • Data Cleaning
  • DataFrame
  • Linear Regression
  • Grouping
  • Arithmetic
  • Iteration

For job roles

  • R Developer

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Simple, straight-forward technical testing

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