R questions

Question 1

what is R

Answer 1

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

Question 2

List out some of the function that R provides?

Answer 2

The function that R provides are

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

Question 3

Explain how you can start the R commander GUI?

Answer 3

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

Question 4

In R how you can import Data?

Answer 4

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

Question 5

Mention what does not ‘R’ language do?

Answer 5

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

Question 6

Explain how R commands are written?

Answer 6

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

Question 7

How can you save your data in R?

Answer 7

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.

Question 8

Mention how you can produce co-relations and covariances?

Answer 8

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

Question 9

Explain what is t-tests in R?

Answer 9

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

Question 10

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

Answer 10

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.

Question 11

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

Answer 11

R has data structures like

Vectors
Matrices
Arrays
Data frames

Question 12

Explain general format of Matrices in R?

Answer 12

General format is

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

Question 13

In R how missing values are represented ?

Answer 13

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

Question 14

Explain what is transpose?

Answer 14

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.

Question 15

Explain how data is aggregated in R?

Answer 15

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.

Question 16

What is the function used for adding datasets in R?

Answer 16

rbind function can be used to join two data frames (datasets). The two data frames must have the same variables, but they do not have to be in the same order.

Question 17

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

Answer 17

In R, subset() functions help you to select variables and observations while through sample() function you can choose a random sample of size n from a dataset.

Question 18

Explain how you can create a table in R without external file?

Answer 18

Use the code

myTable = data.frame()
edit(myTable)
This code will open an excel like spreadsheet where you can easily enter your data.