**1. How R commands are written?**

By using # at the starting of the line of code like #division commands are written.

**2. What is t-tests() in R?**

It is used to determine that the means of two groups are equal or not by using t.test() function.

**3.What are the disadvantages of R Programming?**

The disadvantages are:-

- Lack of standard GUI
- Not good for big data.
- Does not provide spreadsheet view of data.

**4.What is the use of With () and By () function in R?**

with() function applies an expression to a dataset.

#with(data,expression)

By() function applies a function t each level of a factors.

#by(data,factorlist,function)

**5. In R programming, how missing values are represented?**

In R missing values are represented by NA which should be in capital letters.

**6. What is the use of subset() and sample() function in R?**

Subset() is used to select the variables and observations and sample() function is used to generate a random sample of the size n from a dataset.

**7. Explain what is transpose.**

Transpose is used for reshaping of the data which is used for analysis. Transpose is performed by t() function.

**8. What are the advantages of R?**

- The advantages are:-
- It is used for managing and manipulating of data.
- No license restrictions
- Free and open source software.
- Graphical capabilities of R are good.
- Runs on many Operating system and different hardware and also run on 32 & 64 bit processors etc.

Now that you are aware of the benefits of R programming

**9. What is the function used for adding datasets in R?**

For adding two datasets rbind() function is used but the column of two datasets must be same.

Syntax: rbind(x1,x2……) where x1,x2: vector, matrix, data frames.

**10. How you can produce co-relations and covariances?**

Cor-relations is produced by cor() and covariances is produced by cov() function.

**11.What is difference between matrix and dataframes?**

Dataframe can contain different type of data but matrix can contain only similar type of data.

**12.What is difference between lapply and sapply?**

lapply is used to show the output in the form of list whereas sapply is used to show the output in the form of vector or data frame

**13. What is the difference between seq(4) and seq_along(4)?**

Seq(4) means vector from 1 to 4 (c(1,2,3,4)) whereas seq_along(4) means a vector of the length(4) or 1(c(1)).

**14. Explain how you can start the R commander GUI.**

rcmdr command is used to start the R commander GUI.

**15. What is the memory limit of R?**

In 32 bit system memory limit is 3Gb but most versions limited to 2Gb and in 64 bit system memory limit is 8Tb.

**16.How many data structures R has?**

There are 5 data structure in R i.e. vector, matrix, array which are of homogenous type and other two are list and data frame which are heterogeneous.

**17. Explain how data is aggregated in R.**

There are two methods that is collapsing data by using one or more BY variable and other is aggregate() function in which BY variable should be in list.

**18. Explain how you can start the R commander GUI? **

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

**19. What are R packages?**

Packages are the collections of data, R functions and compiled code in a well-defined format and these packages are stored in library.

**20. What is the workspace in R?**

Workspace is the current R working environment which includes any user defined objects like vector, lists etc.

**21. What is the function which is used for merging of data frames horizontally in R?**

Merge()function is used to merge two data frames

Eg. Sum<-merge(data frame1,data frame 2,by=’ID’.

**22. what is the function which is used for merging of data frames vertically in R?**

rbind() function is used to merge two data frames vertically.

Eg.

Sum<- rbind(data frame1,data frame 2)

**23. What is the power analysis?**

It is used for experimental design .It is used to determine the effect of given sample size.

**24. Which package is used for power analysis in R?**

Pwr package is used for power analysis in R.

**25. Which method is used for exporting the data in R?**

There are many ways to export the data into another formats like SPSS, SAS , Stata , Excel Spreadsheet.

**26. Which packages are used for exporting of data?**

For excel xlsReadWrite package is used and for sas,spss ,stata foreign package is implemented.

**27. How impossible values are represented in R?**

In R NaN is used to represent impossible values.

**28. Which command is used for storing R object into a file?**

Save command is used for storing R objects into a file.

Syntax: >save(z,file=”z.Rdata”)

**29. Which command is used for restoring R object from a file?**

load command is used for storing R objects from a file.

Syntax: >load(”z.Rdata”)

**30. What is the use of coin package in R?**

Coin package is used to achieve the re randomization or permutation based statistical tests.

**31. Which function is used for sorting in R?**

order() function is used to perform the sorting.

**32. What is the use of tapply?**

IOS-6.1.3

**33. What happens when the application object does not handle an event?**

The event will be dispatched to your delegate for processing.

**34. Explain app specific objects which store the app contents.**

The app specific objects are Data model objects that store app’s contents.

**35. Explain the purpose of using UIWindow object?**

UIWindow object coordinates the one or more views presenting on the screen.

**36. Tell me the super class of all view controller objects.**

UIView Controller class.

**37. ****How to create axes in the graph?**

Using axes() function custom axes are created.

**38. What is the use of abline() function?**

abline() function is add the reference line to a graph.

Syntax:-

abline(h=yvalues, v=xvalues)

**39. Why vcd package is used?**

vcd package provides different methods for visualizing multivariate categorical data.

**40. What is GGobi?**

GGobi is an open source program for visualization for exploring high dimensional typed data.

**41. What is iPlots?**

It is a package which provide bar plots, mosaic plots, box plots, parallel plots, scatter plots and histograms.

**42. What is the use of lattice package?**

lattice package is to improve on base R graphics by giving better defaults and it have the ability to easily display multivariate relationships.

**43. What is fitdistr() function?**

It is used to provide the maximum likelihood fitting of univariate distributions. It is defined under the MASS package.

**44. Which data structures are used to perform statistical analysis and create graphs.**

Data structures are vectors, arrays, data frames and matrices.

**45. What is the use of sink() function?**

It defines the direction of output.

**46. Why library() function is used?**

This function is used to show the packages which are installed.

**47. Why search() function is used?**

By this function we see that which packages are currently loaded.

**48.On which type of data binary operators are worked?**

Binary operators are worked on matrices, vectors and scalars.

**49. What is the use of doBY package?**

It is used to define the desired table using function and model formula.

**50. Explain how you can start the R commander GUI?**

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