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Programming Articles
Page 2320 of 2547
How to extract p-value and R-squared from a linear regression in R?
We can use regression model object name with $r.squared to find the R-squared and a user defined function to extract the p-value.ExampleExtracting R-Squared> x y LinearRegression summary(LinearRegression)$r.squared [1] 0.2814271Extracting p-value> Regressionp
Read MoreHow to sort a data frame in R by multiple columns together?
We can sort a data frame by multiple columns using order function.ExampleConsider the below data frame −> df df x1 x2 x3 x4 1 Hi A 4 9 2 Med B 7 5 3 Hi D 5 7 4 Low C 3 4Let’s say we want to sort the data frame by column x4 in descending order then by column x1 in ascending order.It can be done follows −> df[with(df, order(-x4, x1)), ] x1 x2 x3 x4 1 Hi A 4 9 3 Hi D 5 7 2 Med B 7 5 4 Low C 3 4We can do ...
Read MoreHow can we serialize a list of objects using flexjson in Java?
The Flexjson is a lightweight library for serializing and deserializing Java objects into and from JSON format. We can serialize a list of objects using the serialize() method of JSONSerializer class. This method can perform a shallow serialization of the target instance. We need to pass a list of objects of List type as an argument to the serialize() method.Syntaxpublic String serialize(Object target)Exampleimport flexjson.JSONSerializer; import java.util.*; public class JsonSerializeListTest { public static void main(String[] args) { JSONSerializer serializer = new JSONSerializer().prettyPrint(true); // pretty print JSON ...
Read MoreWhen can we call @JsonAnyGetter and @JsonAnySetter annotations in Java?
The @JsonAnyGetter annotation enables to use a Map as a container for properties that we want to serialize to JSON and @JsonAnySetter annotation instructs Jackson to call the same setter method for all unrecognized fields in the JSON object, which means that all fields that are not already mapped to a property or setter method in the Java object.Syntaxpublic @interface JsonAnyGetter public @interface JsonAnyGetterExampleimport java.io.*; import java.util.*; import com.fasterxml.jackson.core.*; import com.fasterxml.jackson.databind.*; import com.fasterxml.jackson.annotation.*; public class JsonAnyGetterAndJsonAnySetterTest { public static void main(String args[]) throws JsonGenerationException, JsonMappingException, IOException { Employee emp1 = new ...
Read MoreConvert CSV to JSON using the Jackson library in Java?
A Jackson is a Java JSON API that provides several different ways to work with JSON. We can convert CSV data to JSON data using the CsvMapper class, it is specialized ObjectMapper, with extended functionality to produce CsvSchema instances out of POJOs. We can use the reader() method for constructing ObjectReader with default settings. In order to convert this, we need to import the com.fasterxml.jackson.dataformat.csv package.In the below example, convert a CSV to JSON.Exampleimport java.io.*; import java.util.*; import com.fasterxml.jackson.databind.*; import com.fasterxml.jackson.dataformat.csv.*; public class CsvToJsonTest { public static void main(String args[]) throws Exception { ...
Read MoreHow to deserialize a JSON array to list generic type in Java?
The Gson library provides a class called com.google.gson.reflect.TypeToken to store generic types by creating a Gson TypeToken class and pass the class type. Using this type, Gson can able to know the class passed in the generic class.Syntaxpublic class TypeToken extends ObjectWe can deserialize a JSON array to a generic type of list in the below exampleExampleimport java.lang.reflect.Type; import java.util.*; import com.google.gson.*; import com.google.gson.reflect.*; public class JSONArrayToListTest { public static void main(String args[]) throws Exception { String jsonStr = "[{"name":"Adithya", "course":"Java"}, " + "{"name":"Ravi", "course":"Python"}]"; ...
Read MoreC++ Program to Compute the Area of a Triangle Using Determinants
In this section we will see how to find the area of a triangle in 2D coordinate space using matrix determinants. In this case we are considering the space is 2D. So we are putting each points in the matrix. Putting x values at the first column, y into the second and taking 1 as the third column. Then find the determinant of them. The area of the triangle will be half of the determinant value. If the determinant is negative, then simply take the absolute value of it.$$Area\:=\:absolute\:of\begin{pmatrix}\frac{1}{2} \begin{vmatrix} x_1\:\:y_1\:\:1 \ x_2\:\:y_2\:\:1 \ x_3\:\:y_3\:\:1 \end{vmatrix} \end{pmatrix}$$Here we are assuming ...
Read MoreRename multiple files using Java
Following is the code to rename multiple files using Java −Exampleimport java.io.File; import java.io.IOException; public class Demo{ public static void main(String[] argv) throws IOException{ String path_to_folder = "path\to\folder\where\multiple\files\are\present"; File my_folder = new File(path_to_folder); File[] array_file = my_folder.listFiles(); for (int i = 0; i < array_file.length; i++){ if (array_file[i].isFile()){ File my_file = new File(path_to_folder + "" + array_file[i].getName()); String long_file_name = array_file[i].getName(); String[] my_token = long_file_name.split("\s"); ...
Read MoreJar files in Java
JAR is a file format that helps in aggregating Java class file, along with its associated metadata and resources into a single file.Creation of a JAR file − The jar cf command can be used, where ‘cf’ means creating the file.jar cf jar_file_name files_to_compressOnce a jar file has been created, a default manifest file is also created. Only one manifest file is present in a specific archive, and it will have the extension ‘mf’ and will be in the pathname. Thismanifest file helps give information about the files that have been compressed/present in the package.Viewing a JAR file − The ...
Read MoreInteresting Facts about Java
Java was built by sheer accident, a team of developers were busy building a set top box, and began cleaning C++. When they were winding up these changes, they ended up discovering Java and its runtime environment.Many of you might be aware of this, but for those who aren’t, Java wasn’t the original name that was decided for this language. It was ‘Oak’. Sun Marketing system changed the name later when they realized that a company named ‘Oak’ existed.It is a widely used language all over the world, and is considered to be a favourite amongst the developer group, and ...
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