# R Online Test

## For Jobseekers

Practice your skills and earn a certificate of achievement when you score in the top 25%.

Take a Practice Test## For Companies

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Sign Up to Offer this Test## 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

Implement the function *findRoots* to find the roots of the quadratic equation: ax^{2} + 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 2x^{2} + 10x + 8 = 0 are -1 and -4.

The data science team in a telecom company needs an R function that will load a CSV file into a *DataFrame *and format it so that it can be used with already existing R code.

The *loadData *function accepts a path to a file or a *textConnection* that points to a CSV file. The CSV file doesn't contain headers and has two columns, the first is a decimal number and the second one is a string. The first column represents an *id *and the second column represents a *color*. Some rows in the CSV file contain "0" instead of "yellow" in the second column.

The function should return a *DataFrame *after:

- loading data from the CSV into the
*DataFrame*. - replacing all "0" in the second column with "yellow".
- renaming the first column to "id" and the second column to "color".

For example, the following code:

```
text = "0.0,blue\n1.0,0\n2.0,red"
print(loadData(text))
```

Should print:

```
id color
1 0 blue
2 1 yellow
3 2 red
```

## For jobseekers: get certified

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

Take a Certification Test## Sample silver certificate

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## For companies: premium questions

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### 5 more premium R questions

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

### Skills and topics tested

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

### For job roles

- R Developer

### Sample candidate report

## What others say

Simple, straight-forward technical testing

TestDome is simple, provides a reasonable (though not extensive) battery of tests to choose from, and doesn't take the candidate an inordinate amount of time. It also simulates working pressure with the time limits.

Jan Opperman, Grindrod Bank

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