Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Since operations with data.table are sometimes faster than the data frames, we might want to convert a data frame to a data.table object. The main difference between data frame and data.table is that data frame is available in the base R but to use data.table we have to install the package data.table. We can do this with the help setDT function in the data.table package.ExampleConsider the below data frame −> set.seed(1) > x1 x2 x3 x4 x5 df df x1 x2 x3 x4 x5 1 -0.1264538 1.7189774 2 6 9.959193 2 0.6836433 1.5821363 3 4 7.477968 3 -0.3356286 ... Read More
In a plot, the axes labels help us to understand the range of the variables for which the plot is created. While creating a plot in R using plot function, the axes labels are automatically chosen but we can change them. To do this, firstly we have to remove the axes then add each of the axes with the labels we want and then create the box for the plot.ExampleConsider the below data −> x y plot(x, y)OutputChanging the axes labels for X and Y axes −> plot(x, y, axes=FALSE)+ + axis(side = 1, at = c(2, 5, 10))+ + ... Read More
We might prefer to use row index or column index during the analysis instead of using their numbers, therefore, we can get them with the help of grep function. While dealing with a large data set it becomes helpful because large data sets have large number of rows and columns so it is easier to recall them with their indexes instead of numbers. Specifically, column indexes are needed, on the other hand, rows are required in special cases only such as analysing a particular case.ExampleConsider the below data frame −> set.seed(1) > x1 x2 x3 x4 x5 df head(df, 20) ... Read More
In this section we will see what is the segment tree. Before discussing that, let us see one problem.Suppose we have an array arr[0, …, n-1], We can do following operations −Find the sum of elements from index l to r, where 0 ≤ l ≤ r ≤ n-1Change the value of a specified element of the array to a new value x. We need to do arr[i] = x. The i in range 0 to n – 1.We can solve this problem by using the Segment tree. The segment tree can help us to get the sum and query ... Read More
In this section we will see what is the interval tree. As the name suggests, that the interval trees are the trees which are associated with the intervals. So before discussing about the interval trees, let us see the elementary intervals.An interval is basically a range. So if one interval is written as [a, b] it indicates that the range is starting from a, and ending at b.Now suppose there is an interval [10, 20]. So there are three range values. First one is -∞ to 10, 10 to 20 and finally 20 to ∞Now, suppose we will create second ... Read More
Bar plot is frequently used to analyze the number of times a level of factor variable occurs in a data set and the Y-axis values are crucial to the bar plot. Sometimes these values are not in the form we want, therefore, we want to replace them with the new ones. This can be done with the help of breaks argument of scale_y_continuous function in ggplot2.ExampleConsider the below data frame −> set.seed(1) > x df library(ggplot2)Creating the plot without specifying the Y-axis values −> ggplot(df, aes(x))+ + geom_bar()OutputPlotting with new Y-axis values −> ggplot(df, aes(x))+ + geom_bar()+ + scale_y_continuous(breaks=c(0, 2, ... Read More
Here we will see, how to perform the deletion of a node from B+ Tree. Suppose we have a B+ Tree like below 7minus;Example of B+ Tree −Deletion has two parts. At first we have to find the element. That strategy is like the querying. Now for deletion, we have to care about some rules. One node must have at-least m/2 elements. So if we delete, one element, and it has less than m-1 elements remaining, then it will adjust itself. If the entire node is deleted, then its children will be merged, and if their size is same as ... Read More
In Text analysis, we might want to extract characters from a single string or from a vector of strings. This extraction might be required to create a new string with some specific words required for further analysis. We can do this with the help of str_sub function of stringr package.ExampleConsider the below string −> x1 library(stringr) > str_sub(x1, 1, 8) [1] "Removing" > str_sub(x1, 1, 23) [1] "Removing harmful things" > str_sub(x1, 29, 37) [1] " the road" > str_sub(x1, 30, 37) [1] "the road" > str_sub(x1, -58, -51) [1] "Removing" > str_sub(x1, -58, -1) [1] "Removing harmful things from ... Read More
If we want to use columns of a matrix as a vector then we can convert them in a list of vectors. To convert matrix columns to a list of vectors, we first need to convert the matrix to a data frame then we can read it as list. This can be done as as.list(as.data.frame(matrix_name)).ExampleConsider the below matrix −> M M [, 1] [, 2] [, 3] [, 4] [, 5] [1, ] 1 6 11 16 21 [2, ] 2 7 12 17 22 [3, ] 3 8 13 18 23 [4, ] 4 9 14 ... Read More
When we have two categorical variables then each of them is likely to have different number of rows for the other variable. This helps us to understand the combinatorial values of those two categorical variables. We can find such type of rows using count function of dplyr package.ExampleConsider the CO2 data in base R −> head(CO2, 20) > head(CO2, 20) Plant Type Treatment conc uptake 1 Qn1 Quebec nonchilled 95 16.0 2 Qn1 Quebec nonchilled 175 ... Read More