Creating graphs in R

Bhu14 — Thu, 02 Dec 2021 13:39:39 +0000

R is very important to analysts because it has a wide range of techniques for graphically interpreting data. The main styles are: dot plot, density plot (can be classified as histograms and kernel), line graphs, bar graphs (stacked, grouped and simple), pie charts (3D,simple and expounded), line graphs(3D,simple and expounded), box-plots(simple, notched and violin plots), bag-plots and scatter-plots (simple with fit lines, scatter-plot matrices, high-density plots and 3-D plots). The foundational function for creating graphs: plot(). This includes how to build a graph, from adding lines and points to attaching a legend.

The plot() Function:

The plot () function forms many foundations for R's basic graphics operations and serves as a means for creating many different types of graphics. plot () is a placeholder for a generic function or function family. The actual function that is called depends on the class of the object that is called.

The basic syntax for plot() function is
*plot(v, type, col, xlab, ylab) *

v is a vector containing the numeric values.
type takes the value "p" to draw only the points, "l" to draw only the lines and "o" to draw both points and lines.
xlab is the label for x axis.
ylab is the label for y axis.
main is the Title for the chart.
col is used to give colors to both the points and lines.

Examples of plot function :

# Define the cars vector with 5 values 
cars <- c(1, 3, 6, 4, 9)
# Graph the cars vector with all defaults 
plot(cars)
The default argument of type is points

# Define the cars vector with 5 values 
cars <- c(1, 3, 6, 4, 9)
# Graph cars using blue points with lines 
plot(cars, type="o", col="blue")
# Create a title with a red, bold/italic font 
title(main="Autos",col.main="red", font.main=4)

POINTERS IN C

Bhu14 — Thu, 20 May 2021 10:38:06 +0000

• Variables are allocated memory space in main
memory/primary memory, to store their
values.
• Main memory is partitioned into cells called
memory cells/memory word .
• Each memory word is given address which is
numerical that ranges from 0 , 1, 2 ….• Pointer is a data type
• Value of pointer variable is memory address which is
numerical value
Declaration
int *P1;
P1 is a pointer variable pointing to integer
value of P1 is memory address of int variable
• Address operator
int x;
&x refers to address of x
Address of x can be assigned to a pointer variable
ex: P1=&x

#VOID POINTER

void pointer is a special type of pointer.
Void pointer can point to a variable of any data type,
integer , float ,character.
– The type casting or assignment must be used to turn the
void pointer to a pointer of a concrete data type to which we
can refer.
– limitation is that the pointed data cannot be referenced directly
(the asterisk * operator cannot be used on them) since its length is
always undetermined.

Example

include

int main()
{
int a=5,
double b=3.1415;
void vp;
vp=&a;
printf(“\n a= %d”, *((int)vp)); // type casting to int pointer
vp=&b;
printf(“\n a= %d”, *((double *)vp));
// typecasting to double pointer
return 0;
}
OUTPUT:
a= 5
b= 3.141500

One dimensional Arrays & pointers:

• Array name is address of first element. So array name
is a pointer
• We can access array elements using array name
without using subscript
Int x[5];
x refers to address of 0th element
x+1 refers to address of 1st
element
…..
x+n-1 refers to address of (n-1)th or last element

// accessing array elements using array name which is a pointer

include

main()
{
int a[5]={10,20,30,40,50};
clrscr();
printf("address of a[0]=%p a[1]=%p a[2]=%p\n",&a[0],&a[1],&a[2]);
printf("address of the first element of array=%p\n",a);
printf("value of first element=%d value =%d\n",a[0],a);
printf("value of second element=%d value=%d\n",a[1],(a+1));
printf("value of last element=%d value=%d\n",a[4],*(a+4));
return;
}

Accessing array elements using pointer

include

int main()
{
int i,a[7]={1,2,3,4,5,6,7};
int p;
p=a; // array name is a pointer to the first element
for(i=0; i<7; i++)
printf("%d\t",(p+i)); //adding i value to pointer p
return(0);
}

Operations on pointer variables:

• Pointer variable can be assigned with NULL
ex: int *x=NULL
• Pointer variable can be initialized with another pointer or with address of
another variable
Ex:
float x;
float *p1=&x, *p2=p1;
• Integer constant can be added to a pointer. This is useful for accessing
array elements
Ex:
int a[5]={1,2,3,4,5}
int *p1=a;
p1=p1+2 refer to third element of array

DEV Community: Bhu14

Creating graphs in R

The plot() Function:

POINTERS IN C

include

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