#### Top 15 R language Interview questions

**1) Explain what is R?**

R is data analysis software which is used by analysts, quants, statisticians, data scientists and others.

**2) List out some of the function that R provides?**

The function that R provides are

- Mean
- Median
- Distribution
- Covariance
- Regression
- Non-linear
- Mixed Effects
- GLM
- GAM. etc.

**3) Explain how you can start the R commander GUI?**

Typing the command, (“Rcmdr”) into the R console starts the R commander GUI.

**4) In R how you can import Data?**

You use R commander to import Data in R, and there are three ways through which you can enter data into it

- You can enter data directly via Data New Data Set
- Import data from a plain text (ASCII) or other files (SPSS, Minitab, etc.)
- Read a data set either by typing the name of the data set or selecting the data set in the dialog box

**5) Mention what does not ‘R’ language do?**

- Though R programming can easily connects to DBMS is not a database
- R does not consist of any graphical user interface
- Though it connects to Excel/Microsoft Office easily, R language does not provide any spreadsheet view of data

**6) Explain how R commands are written?**

In R, anywhere in the program you have to preface the line of code with a #sign, for example

- # subtraction
- # division
- # note order of operations exists

**7) How can you save your data in R?**

To save data in R, there are many ways, but the easiest way of doing this is

Go to Data > Active Data Set > Export Active Data Set and a dialogue box will appear, when you click ok the dialogue box let you save your data in the usual way.

**8) Mention how you can produce co-relations and covariances?**

You can produce co-relations by the cor () function to produce co-relations and cov () function to produce covariances.

**9) Explain what is t-tests in R?**

In R, the t.test () function produces a variety of t-tests. T-test is the most common test in statistics and used to determine whether the means of two groups are equal to each other.

**10) Explain what is With () and By () function in R is used for?**

- With() function is similar to DATA in SAS, it apply an expression to a dataset.
- BY() function applies a function to each level of factors. It is similar to BY processing in SAS.

**11) What are the data structures in R that is used to perform statistical analyses and create graphs?**

R has data structures like

- Vectors
- Matrices
- Arrays
- Data frames

**12) Explain general format of Matrices in R?**

General format is

Mymatrix< - matrix (vector, nrow=r , ncol=c , byrow=FALSE, dimnames = list ( char_vector_ rowname, char_vector_colnames))

**13) In R how missing values are represented ?**

In R missing values are represented by NA (Not Available), why impossible values are represented by the symbol NaN (not a number).

**14) Explain what is transpose?**

For re-shaping data before, analysis R provides various method and transpose are the simplest method of reshaping a dataset. To transpose a matrix or a data frame t () function is used.

**15) Explain how data is aggregated in R?**

By collapsing data in R by using one or more BY variables, it becomes easy. When using the aggregate() function the BY variable should be in the list.

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