# R Online Test

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## For Jobseekers

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## For Companies

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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

Easy
15 min
code
Public
R
DataFrame

• 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.

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),
nrow=2,
ncol=2)

Should print:

```  id        name  password
1  1     JohnDoe 987340123
2  2 AnnFranklin 187031122
```
Easy
10 min
code
Public
R
Arithmetic

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:

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.

## For jobseekers: get certified

Earn a free certificate by achieving top 25% on the R test with public questions.

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Java and SQL
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### Skills and topics tested

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

• R Developer

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