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The concatenation of string vectors will create combination of the values in the vectors thus, we can use them for interaction between/among the vectors. In R, we can use expand.grid along with apply to create such type of combinations as shown in the below examples.Example 1 Live Demox1
Instructors/educators often need to teach missing value imputation to their students; hence they require datasets that contains some missing values or they need to create one. We also have some data sets with missing values available in R such as airquality data in base R and food data in VIM package. There could be many other packages that contain data sets with missing values but it would take a lot of time to explore them. Thus, we have shared the example of airquality and some data sets from VIM package.Example 1 Live Demohead(airquality, 20)Output Ozone Solar.R Wind Temp Month Day 1 41 ... Read More
If a column in an R data frame has only two values 0 and 1 then we call it a binary column but it is not necessary that a binary column needs to be defined with 0 and 1 only but it is a general convention. To detect a binary column defined with 0 and 1 in an R data frame, we can use the apply function as shown in the below examples.ExampleConsider the below data frame − Live Demox1
Problem:You want to display open cursors in Oracle.SolutionWe can query the data dictionary to determine the number of cursors that are open per session. "V$SESSION" provides a more accurate number of the cursors currently open than "V$OPEN_CURSOR".Exampleselect a.value , c.username , c.machine , c.sid , c.serial# from v$sesstat a , v$statname b , v$session c where a.statistic# = b.statistic# and c.sid = a.sid and b.name = 'opened cursors current' and a.value != 0 and c.username IS NOT NULL order by 1, 2;The OPEN_CURSORS initialization parameter determines the maximum number of cursors a session can have open.Read More
Problem:You want to identify the SQL statements responsible for the most waits in your database.SolutionWe can use below SQL statement to identify SQL causing problem.The below query will rank SQL statements that ran during the past 30 minutes and display them as per the total time waited by each query.ExampleSELECT ash.user_id, u.username, s.sql_text, SUM(ash.wait_time + ash.time_waited) ttl_wait_time FROM v$active_session_history ash, v$sqlarea s, dba_users u WHERE ash.sample_time BETWEEN sysdate - 60/2880 AND sysdate AND ash.sql_id = s.sql_id AND ash.user_id = u.user_id GROUP BY ash.user_id, s.sql_text, u.username ORDER BY ttl_wait_time ;When you have a performance ... Read More
With INNER JOIN only the matching elements are included in the result set. Non-matching elements are excluded from the result set.With LEFT OUTER JOIN all the matching elements + all the non-matching elements from the left collection are included in the result set.Let us understand implementing Left Outer Join with an example. Consider the following Department and Employee classes. Notice that, Employee Mary does not have a department assigned. An inner join will not include her record in the result set, where as a Left Outer Join will.Examplestatic class Program{ static void Main(string[] args){ var result = Employee.GetAllEmployees() ... Read More
Reflection is the process of describing the metadata of types, methods and fields in a code. The namespace System.Reflection enables you to obtain data about the loaded assemblies, the elements within them like classes, methods and value types. There are numerous classes of System.Reflection but the most commonly used ones are Assembly, AssemblyName, ConstructorInfo, MethodInfo, ParameterInfo, EventInfo, PropertyInfo, and MemberInfo.Examplestatic void Main(string[] args){ TypeInfo myType = typeof(TextInfo).GetTypeInfo(); IEnumerable properties = myType.DeclaredProperties; IEnumerable methods = myType.DeclaredMethods; Console.WriteLine(myType); Console.WriteLine(properties); Console.WriteLine(methods); StringBuilder strBuilder = new StringBuilder(); Console.WriteLine(); strBuilder.Append("The properties are:"); foreach (PropertyInfo p ... Read More
The process of injecting (converting) coupled (dependent) objects into decoupled (independent) objects is called Dependency Injection.Types of Dependency InjectionThere are four types of DI −Constructor InjectionSetter InjectionInterface-based injectionService Locator InjectionInterface InjectionInterface Injection is similar to Getter and Setter DI, the Getter, and Setter DI use default getter and setter but Interface Injection uses support interface a kind of explicit getter and setter which sets the interface property.Examplepublic interface IService{ string ServiceMethod(); } public class ClaimService:IService{ public string ServiceMethod(){ return "ClaimService is running"; } } public class AdjudicationService:IService{ public string ServiceMethod(){ ... Read More
The process of injecting (converting) coupled (dependent) objects into decoupled (independent) objects is called Dependency Injection.Types of Dependency InjectionThere are four types of DI −Constructor InjectionSetter InjectionInterface-based injectionService Locator InjectionSetter InjectionGetter and Setter Injection injects the dependency by using default public properties procedure such as Gettter(get(){}) and Setter(set(){}). Examplepublic interface IService{ string ServiceMethod(); } public class ClaimService:IService{ public string ServiceMethod(){ return "ClaimService is running"; } } public class AdjudicationService:IService{ public string ServiceMethod(){ return "AdjudicationService is running"; } } public class BusinessLogicImplementation{ private IService _client; public IService Client{ ... Read More
Software entities like classes, modules and functions should be open for extension but closed for modifications.Definition − The Open Close Principle states that the design and writing of the code should be done in a way that new functionality should be added with minimum changes in the existing code. The design should be done in a way to allow the adding of new functionality as new classes, keeping as much as possible existing code unchanged.ExampleCode Before Open Closed Principleusing System; using System.Net.Mail; namespace SolidPrinciples.Open.Closed.Principle.Before{ public class Rectangle{ public int Width { get; set; } ... Read More