Programming Articles - Page 1370 of 3366

A binary matrix contains values such as Yes or NO, 1 or 0, or any other two values that represents opposite mostly and the globally accepted logical values are FALSE and TRUE. Therefore, to convert a binary matrix to logical matrix, we can use ifelse function and convert the one category of binary variable to appropriate logical value and for the rest returns the left-out value. This is a very easy task in R, check out the below examples to understand how it can be done.Example1Live Demo> M1 M1Output[, 1] [, 2] [1, ] "No" "Yes" [2, ] "No" "No" ... Read More

When we apply a function using apply family, by default the output is not in the form of a data frame. If we want to preserve the original data frame structure then we need to set the application of the apply family by setting it to the original data frame with single brackets and no arguments as shown in the below examples.Example1Consider the below data frame −Live Demo> df1 df1Output   x1 x2 1  4 2 2  6 2 3  5 2 4  2 1 5  8 4 6  7 2 7  5 3 ... Read More

The mutate function of dplyr package in R can help us to add a new column to a data frame and the benefit of using mutate is that we can decide the position of the new column during the addition. For example, if we have a data frame called df that contains three columns say x, y, a then we can add a new column say z after y using mutate function. To understand how it can be done, check out the below examples.Example1Consider the below data frame −Live Demo> x1 x3 df1 df1Output   x1 x3 1  2  3 2 ... Read More

To find the number of characters in character vector elements or the elements in a character column of an R data frame, we can use nchar function. Therefore, if we want to remove rows that has elements of size less than 3 we would need to use the same function and then subset function will be used to remove the required rows as shown in the below examples.Example1Consider the below data frame −Live Demo> x1 x2 df1 df1Output    x1   x2 1  India 1 2  India 2 3  UK    1 4  UK    2 5  China 1 6 ... Read More

Scope rules are related to the following factors −Accessibility of a variables.Period of existence of a variable.Boundary of usage of variables.Scope rules related to functions are as followsFunction which is a self-contained block that performs a particular task.Variables that are declared within the function body are called local variables.These variables only exist inside the specific function that creates them. They are unknown to other functions and to the main functions too.The existence of local variables ends when the function completes its specific task and returns to the calling point.Example 1Following is the C program for scope rules related to functions ... Read More

To create a frequency table in R, we can simply use table function but the output of table function returns a horizontal table. If we want to read the table in data frame format then we would need to read the table as a data frame using as.data.frame function. For example, if we have a table called T then to convert it into a data frame format we can use the command as.data.frame(T).Example1Live Demo> x1 x1Output[1] 2 0 2 3 2 3 1 2 1 4 0 0 4 4 1 3 1 2 1 3 2 3 2 1 ... Read More

If column is categorical then there can be at least two categories and there is no limit for the total number of categories but it will also depend on the total number of cases. If we have a data frame that contain some categorical columns having more or less categories than 4 then we might want to subset columns having less than four categories. This could be required in situations when we want to subset the data biasedly or have some predefined data characteristics that allows this change. The subset of such columns can be done with the help of ... Read More

The character values can be stored in uppercase, lowercase, or a mixture of the two. If we have values that are either in uppercase or the mixture of lower and upper then we can convert those character values to only lowercase by using tolower function. We simply need to pass the vector or column of the data frame inside the tolower function as shown in the below examples.Example1Consider the below data frame −Live Demo> x1 y1 df1 df1Output   x1     y1 1  C  -0.1036851 2  C  -0.6176530 3  B   0.5763786 4  A   0.1943794 5  C   1.1196470 ... Read More

An array is a group of related items that store with a common name.SyntaxThe syntax is as follows for declaring an array −datatype array_name [size];InitializationAn array can also be initialized at the time of declaration −int a[5] = { 10, 20, 30, 40, 50};Reversing array in CWe can reverse array by using swapping technique.For example, if 'P' is an array of integers with four elements −P[0] = 1, P[1] = 2, P[2] = 3 and P[3]=4Then, after reversing −P[0] = 4, P[1] = 3, P[2] = 2 and P[3]=1ExampleFollowing is the C program to reverse an array −#include int ... Read More

Functions are broadly classified into two types, which are as follows −Predefined functionsUser defined functionsPredefined (or) library functionsThese functions are already defined in the system libraries.Programmer will reuse the already present code in the system libraries to write error free code.But to use the library functions, user must be aware of syntax of the function.Example −sqrt() function is available in math.h library and its usage is −y= sqrt (x) x number must be positive eg: y = sqrt (25) then ‘y’ = 5printf ( ) present in stdio.h library.clrscr ( ) present in conio.h library.ExampleGiven below is the C program ... Read More