To create data frame using nested list elements, we would need to unlist the list elements and store them in a matrix then read as a data frame using data.frame function. For example, if we have a nested called LIST then the data frame can be created by using the command −data.frame(matrix(unlist(LIST),ncol=”No of columns we want”,byrow=F))Check out the below example to understand how it works.Example Live DemonestedList

To subset an R data frame based on string match in two columns with OR condition, we can use grepl function with double square brackets and OR operator |. For example, if we have a data frame called df that contains two string columns say x and y then subsetting based on a particular string match in any of the columns can be done by using the belowSyntaxdf[grepl("text",df[["x"]])|grepl("text",df[["y"]]),]Check out the below examples to understand how it works.Example1Consider the below data frame − Live Demof1

To change the default point size of geom_point, we need to use update_geom_defaults function. Specifically, for the change of point size the syntax will be as follows −update_geom_defaults("point",list(size=”value”))Here, we can change the value according to our need.ExampleConsider the below data frame − Live Demox

To find the proportion of each value for a cross tab obtained from a data frame, we can use prop.table function. Suppose we have a data frame called df that contains three columns, two categorical say C1 and C2 and one numerical say Y then the cross tab will be created by using the command xtabs(Y~.,df). Now the proportion of each value can be found by using prop.table(xtabs(Y~.,df),1).Example1Consider the below data frame − Live Demof1

To change the point size in geom_point conditionally, we can define the condition in geom_point with aes and the size using scale_size_manual function of ggplot2 package. For example, if we have a data frame called df that contains two columns say x and y then the scatterplot with different size of points for x values greater than 5 and less than equal to 5 can be drawn by using the below command −ggplot(df, aes(x, y))+geom_point(aes(size=x>5))+scale_size_manual(values=c(4, 7))ExampleConsider the below data frame − Live Demox6))+scale_size_manual(values=c(4, 7)) OutputRead More

To create a list of regression models for predefined vectors, we can create a blank list and then use the for loop to create the list of regression models. For example, if we have two vectors say x and y, and we want to create a list of regression model between x and y then we create a blank list using list() and perform for loop a particular number of times as shown in the below examples.Example1 Live Demox

To add approximately equal sign in a plot using ggplot2, we can use tilde sign twice as ~~ in geom_text function of ggplot2 package. For example, we can do this by using the following syntax geom_text(aes(label="NULL%~~%")). Check out the below example to understand how it works.ExampleConsider the below data frame − Live Demox

Increment operator (++)It is used to increment the value of a variable by 1. There are two types of increment operators, pre-increment and post-increment.The increment operator is placed before the operand in pre-increment and the value is first incremented and then the operation is performed on it.For example, z = ++a; a= a+1 z=aThe increment operator is placed after the operand in post-increment and the value is incremented after the operation is performed.For example, z = a++; z=a a= a+1Example 1Following is an example for pre-increment operator − Live Demomain ( ){    int A= 10, Z;    Z= ++A;   ... Read More

ProblemHow to identify a total number of upper-case alphabets in a string using C Programming?SolutionThe logic we used to count number of upper-case letters in a sentence is as follows −for(a=string[0];a!='\0';i++){    a=string[i];    if (isupper(a)){       counter=counter+1;       //counter++;    } }Example 1 Live Demo#include #include void main(){    //Declaring integer for number determination, string//    int i=0;    char a;    char string[50];    int counter=0;    //Reading User I/p//    printf("Enter the string :");    gets(string);    //Using For loop and predefined function to count upper case alpha's//    for(a=string[0];a!='\0';i++){       a=string[i]; ... Read More

ProblemWrite a C program to display and add the elements using dynamic memory allocation functions.SolutionIn C, the library function malloc allocates a block of memory in bytes at runtime. It returns a void pointer, which points to the base address of allocated memory and it leaves the memory uninitialized.Syntaxvoid *malloc (size in bytes)For example, int *ptr;ptr = (int * ) malloc (1000);int *ptr;ptr = (int * ) malloc (n * sizeof (int));Note − It returns NULL, if the memory is not free.Example Live Demo#include #include void main(){    //Declaring variables and pointers, sum//    int numofe, i, sum=0;    int *p; ... Read More