Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
If we have categorical data in a data.table object and some values are duplicate then we might want to extract unique rows from that object.To extract unique rows by categorical column of a data.table object, we can use unique function and define the columns with by argument as shown in the below examples. To understand how the extraction is done check out the below examples.Example 1Following snippet creates a data.table object −library(data.table) grp
The diagonal elements of a matrix occur at the position where column and row indices are same hence, we can make use of those indices to extract diagonal elements of a matrix if we do not want to use diag function.For example, if we have a matrix called M then diagonal elements of M can be extracted by using the command given below − M[row(M)==col(M)]Check out the below examples to understand how it works.Example 1Following snippet creates a matrix −M1
To create a data frame column with equally spaced values between 0 and 1, we can use ppoints function. For example, if we want to create a data frame df with hundred equally spaced values between 0 and 1 then we can use the below mentioned command −df
To save the str output as a string in R, we can use capture.output function along with str function.For example, if we have a data frame called df and we want to store the str output of df as a string then we can use the command given below −capture.output(str(df))It would be better if we save it in an object as str_df
To find the moving standard deviation in an R data frame, we can make use of rollapply function of zoo package.For example, if we have a data frame called df and we want to find the 2 moving standard deviations then we can use the below given command −rollapply(df,width=2,FUN=sd,fill=0,align="r")Example 1Following snippet creates a sample data frame −x1
To separate first text value and the remaining text in an R, we can follow the below steps −First of all, create a vector.Then, use str_split function from stringr package to separate first text value and the remaining text.ExampleCreate the vectorLet’s create a vector as shown below −x
To create sequential index value for binary column assigning 0 to FALSE values in R data frame, we can follow the below steps −First of all, create a data frame with binary column.Then, use rle function along with sequence and lengths function to create sequential index column.ExampleCreate the data frameLet’s create a data frame as shown below −x
To convert first letter of multiple string columns into capital in data.table object in R, we can follow the below steps −First of all, create a data.table object with string columns.Then, use sub function along with mutate_each function of dplyr package to convert first letter into capital in string columns.ExampleCreate the data.table objectLet’s create a data.table object as shown below −library(data.table) Names
To generate a repeated values vector with each value in output selected randomly in R, we can use replicate function. The replicate function will repeat the vector values up to the number of times we want and each value will be randomly selected. To understand how it works, check out the below examples.Example 1Using replicate function to create a vector of exponential random variable of size 10 −x1
To change the background color of base R plot region, we can follow the below steps −First of all, create a plot in base R to understand the difference.Then, use par function with bg argument where you can put color name and then create the same plot.ExampleCreate the plotLet’s create a barplot in base R as shown below −x