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Programming Articles
Page 10 of 2545
How to add or multiply each element of a matrix to the corresponding element of another matrix in R, if these matrices are stored as a list?
Basic mathematical operations such as addition, subtraction, multiplication, and division are common for matrices and we often do that but if the matrices are stored as a list in R then these basic calculations are done differently as they are not direct objects. To add or multiply the matrices in a list, we can use Reduce function with the plus (+) or multiply (*) sign and the list name.ExampleMatrices_List
Read MorePHP sqrt() Function
Definition and UsageThe sqrt() function returns square root of a positive float number. Since square root for negative number is not defined, it returns NAN. This is one of the most commonly used functions.This function always returns a floating point number.Syntaxsqrt ( float $arg ) : floatParametersSr.NoParameter & Description1arga number whose square root is to be obtainedReturn ValuesPHP sqrt() function returns square root of the given arg number. For negative number, the function returns NAN.PHP VersionThis function is available in PHP versions 4.x, PHP 5.x as well as PHP 7.x.ExampleOutputThis will produce following result −sqrt(-1) = NAN
Read MoreHow to create a new data frame for the mean of rows of some columns from an R data frame?
Finding row means help us to identity the average performance of a case if all the variables are of same nature and it is also an easy job. But if some of the columns have different type of data then we have to extract columns for which we want to find the row means. Therefore, we can create a new data frame with row means of the required columns using rowMeans function.Examplerow_means_3.4_cols_df
Read MorePHP srand() Function
Definition and UsageThe srand() function is used to seed the random number generaror. Seeding initializes the random number generator. Most random number generators need initial seeding. In PHP, use of srand() function is optional as it is done automatically.This function doen't have any return value.Syntaxsrand ([ int $seed ] ) : voidParametersSr.NoParameter & Description1seedan integer to be used as seed. If not given, a random number is givenReturn ValuesThis function doesn't return any value.PHP VersionThis function is available in PHP versions 4.x, PHP 5.x as well as PHP 7.x.ExampleOutputThis may produce following result−rand()=548287992
Read MorePHP tan() Function
Definition and UsageThe tan() function returns the tangent ratio of given angle in radians. In trigonometry, tangent of an angle is defined as ratio of lengths of opposite side and adjacent side.tan(x) = opposite/adjacenttangent of an angle is also defined as ratio of its sine and cosinetan(x) = sin(x)/cos(x)If x=45 degree, tan(x) = 1 as in a right angled traingle, opposite and adjacent sides are qual.This function returns a float value.Syntaxtan ( float $arg ) : floatParametersSr.NoParameter & Description1argA floating point value that represents angle in radiansReturn ValuesPHP tan() function returns tangent ratio of given parameter.PHP VersionThis function is available in PHP versions 4.x, PHP ...
Read MoreHow to a split a continuous variable into multiple groups in R?
Splitting a continuous variable is required when we want to compare different levels of a categorical variable based on some characteristics of the continuous variable. For example, creating the salary groups from salary and then comparing those groups using analysis of variance or Kruskal-Wallis test. To split a continuous variable into multiple groups we can use cut2 function of Hmisc package −Exampledf$Salary_Group
Read MoreMatching Nonprintable Characters using Java regex
There are 7 common non printable characters used in general and each character has its own hexadecimal representation.NamecharactersHexa-decimal representationbell\a0x07Escape\e0x1BForm feed\f0x0CLine feed0x0ACarriage return\r0X0DHorizontal tab\t0X09Vertical tab\v0X0BExample 1import java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class RegexExample1 { public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.println("Enter input text: "); String input = sc.nextLine(); String regex = "\x09"; //Creating a pattern object Pattern pattern = Pattern.compile(regex); //Matching the compiled pattern in the String Matcher matcher = ...
Read MoreHow to deal with the error “Error in int_abline---plot.new has not been called yet” in R?
The above error means plot is not being created yet hence abline function cannot be used to draw anything on the plot. Therefore, a plot needs to be created first to use abline function for creating a line or any other thing. Mostly, abline is used to create regression line on the plot, thus we need to create a scatterplot first before using abline.Exampleabline(lm(y~x))Output
Read MoreHow to create correlation matrix plot in R?
To create a correlation matrix plot, we can use ggpairs function of GGally package. For example, if we have a data frame called df that contains five columns then the correlation matrix plot can be created as ggpairs(df). A correlation matrix plot using ggpairs display correlation value as well as scatterplot and the distribution of variable on diagonal.Examplelibrary(GGally) ggpairs(df)Output
Read MoreProgram to check whether one value is present in BST or not in Python
Suppose we have a binary search tree and another input called val, we have to check whether val is present in the tree or not.So, if the input is likeval = 7, then the output will be True, as 7 is present in the tree.To solve this, we will follow these steps−Define a function solve() . This will take root, valif root is null, thenreturn Falseif data of root is same as val, thenreturn Trueif data of root < val, thenreturn solve(left of root, val)return solve(right of root, val)Let us see the following implementation to get better understanding−class TreeNode: ...
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