#### R System Interview Questions

##### Q1). What is R?

R is an interpreted programing language and software environment that is used to analyze statistical information, graphical representation, reporting and data modelling. It is developed by Ross Ihaka and Robert Gentleman at Auckland University. It is an application and Software programming language.

##### Q2). What are the Features of R?

Following are the features of the R Programing language:

- It is an open-source software environment.
- R programming is a simple and powerful programing language.
- R is used for data analysis, or we can say data analysis software.
- It has solid graphical capabilities.
- It performs a fast calculation.

##### Q3). What are the packages which are used for data manipulation?

Following are the packages which are used for data manipulation:

- Mi
- MICE
- inputR
- Hmisc
- missFores
- Amelia

##### Q4). What is initialize() function in R?

It is used to initialize the private data member while declaring the object.

##### Q5). What is the Random Walk Model?

Random walk model is the example of non-stationary process.

Simulation of Random walk model in R is:

##### arima.sim(model=list(order=c(0,1,0)),n=40)->rwts.plot(rw)

##### Q6). What is White Noise Model?

The white Noise Model is an example of a non-stationary process. It is a basic time series model. It has a fixed constant mean, fixed constant variance and no correlation over time.

Simulation of White Noise Model:

##### arima.sim(model=list(order=c(0,0,0)),n=50)->wn

##### Q7). Difference between Vector, List, Matrix, and Data frame.

##### Vector-

It is a sequence of elements that share the same data types. It is a basic data structure that plays an essential role in R programming.

##### List-

It is an object with different types of elements like string, numbers, vectors, and another list inside.

##### Matrix-

It is a two-dimensional data structure. It is used to store values of the same data types in the form of rows and columns.

##### Data Frame-

It is used to store data table. It is a generic form of a matrix.

##### Q8).Difference between R and Python.

Followings are the difference between R and Python:

R Programming | Python |
---|---|

It is used to perform Data Analysis and statistics | It is used for production and deployment. |

Scholars and R&D use it | Developers and Programmers use it |

It Runs locally | It is well-integrated with app |

It handles the huge size of Database | It also handles the huge size of Database |

IDE use in R programming is Rstudio | IDE use in Python is Spyder, Ipthon Notebook |

The learning curve in R is difficult at the beginning | The learning curve is linear and smooth. |

The average salary of R programmer is $99.000 | The average salary of a Python developer is $100.000 |

##### Q9). What are the applications of R?

R has many applications like Social Media, IT department, Financial Department and Government uses also. Following are the applications:-

##### Social Media-

##### IT Companies uses R-

- Paytm
- IBM
- Infosys
- TCS
- Wipro

##### Financial Companies use R-

- JP Morgan
- Baja Allianz Insurance
- American Express

##### Government use-

- National Weather services for weather forecasting
- Food and Drug Administration.

##### Q10). What are the Advantages and Disadvantages of R?

##### Advantages

- It is an open-source programing language.
- It is a platform-independent programming language.
- It provides excellent Support for Data Wrangling.
- It is used for machine learning Operations.
- It is continuously growing.

##### Disadvantages

- It has very Basic Security.
- It is Complicated language.
- It does not support dynamic or 3D graphics.
- It is a much slower programming language.

##### Q11). What are the Hadoop integration methods?

Following are the Hadoop Integration methods:

- R Hadoop
- Hadoop Streaming
- RHIPE
- ORCH

##### Q12).Difference between sample() and subset() in R.

##### Sample():

It is used to choose the random sample of size from dataset.

##### Subset():

It is used to choose variable and observations.

##### Q13). Difference between library() and require() function in R.

##### Library() Function-

It shows an error message when the desired package cannot loaded.

##### require() function-

It shows a warning message when particular package is not found and it is used inside the function.

##### Q14).What is t-test?

T-test is the standard test in statistics. It is used to resolve that the mean of two groups are equal or not.

##### Q15).What is use of with() and by() function in R?

With() function is used to apply the expressions to a dataset whereas by() function is used to apply the function to each level of factors.

##### Q16).What is aggregate() function?

To get the aggregate data in R, aggregate() function is use.

##### Q17). What is the use of table() function?

To creating the frequency table in R, table() function is use.

##### Q18). What is doBy package?

To define the desire table with using function and model formula doBy package is use.

##### Q19).What is lattice package?

It is one of the essential data visualization package in R programming. It has multivariate data. It has the functionality to create various plots and graphs.

##### Q20).What is anova() function?

To comparing the nested methods anova() function is use.

##### Q21).What is leaps() function?

It is used to implement the all-subsets regression. It is defined under leaps package.

##### Q22). Full form of MANOVA and its use?

Fill form of MANOVA is Multivariate Analysis of Variance.The use of MANOVA is to test more than one dependent variable together.

##### Q23).Use of forecast package.

It gives us the functions which are used inthe electronic selection of exponential and ARIMA models.

##### Q24).What is FactoMineR?

It is a package that consists of qualitative and quantitative variables. Observations and supplementary variables are also cover in the FactoMineR package.

##### Q25). Full form of SEM and CFA.

The full form of SEM is **“Structural Equation Modeling”** and the full form of CFA is **“Confirmatory Factor Analysis”.**

##### Q26).What are the visualization packages.

Following are the visualization packages:-

- googleVis
- geofacet
- tidyquant
- Plotly
- ggplot2
- Shiny

##### Q27).What is Chi-Square test.

It is used to analyze the contingency table or frequency table established by two categorical tables. The statistical method used to resolve in case two categorical table has a significant correlation between them. R programming provides chisq.test() function to perform chi-square test.

##### Q28). What is Random Forest?

Random Forest is also called Decision Tree Forest. It has higher accuracy than other decision trees. It is used for both classification and regression applications.

##### Q29). What is Histogram?

The Histogram is used to display the numerical variable in the box. It is related to bar chart. The difference between histogram and bar chart is histogram represent numerical value and bar chart represent categorical variables.

##### Q30). What is Pie chart in R?

The pie chart represents values in the form of a wedge of the circle with different colours. R programming language consists a lot of libraries which is used to creating chart and graphs.

##### Q31). What is the output of this expression all(NA==NA)?

[1] NA