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The R online test assesses candidates' knowledge of programming in the R language and their ability to leverage commonly used built-in functions.

It's an ideal test for pre-employment screening. A good R developer needs to be able not only to solve problems using R as the programming language but also recognize when to take advantage of its rich set of built-in functions.

This test requires candidates to be able to solve coding problems in the R language.

#### Sample public questions

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.

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
```

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Certificate #### Skills and topics tested

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

• R Developer

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