R Programing Interview Questions

To evaluate the association between two or more variables we use Correlation. It has Correlation coefficients which are indicators of the strength of the linear relationship between two different variables say

**x**

and **y**

. The correlation coefficient greater than zero indicates that a positive relationship, while a value less than zero indicates that a negative relationship. A negative correlation is also called inverse correlation which is a key concept in the creation of diversified portfolios that can better withstand portfolio volatility. The most common Correlation coefficient is generated by the Pearson product-moment correlation which is used to measure the linear relationship between two variables. The Pearson Correlation is also called parametric correlation.

**Seq(4)**

means vector from **1**

**4 (c(1,2,3,4))**

whereas **seq_along(4)**

means a vector of the **length(4)**

**1(c(1))**

. There are 5 types of sorting algorithms are used which are :

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

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

`>save(z,file=”z.Rdata”)`

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

`>load(”z.Rdata”)`

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

Some packages used for data mining in R :

rpart and caret -

Arules -

GGplot -

tm -

Forecast -

The

**cluster.stats()**

function define in the fpc package that provides a method for comparing the similarity of two cluster solutions using different validation criteria, and the **pvclust()**

function is defined in the pvclust package that provides `p-values`

for hierarchical clustering.
This function defines in the mvnormtest package and produces the **Shapiro-wilk** test to multivariate normality. The

**barlett.test()**

is used to provide a parametric k-sample test of the equality of variances.