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Programming Articles
Page 2279 of 2547
Difference between IOC and Dependency Injection in Spring.
Inversion of control is a design principle which helps to invert the control of object creation.According to the paper written by Martin Fowler , inversion of control is the principle where the control flow of a program is inverted: instead of the programmer controlling the flow of a program, the external sources (framework, services, other components) take control of it. It's like we plug something into something else. He mentioned an example about EJB 2.0.Dependency Injection is a design pattern which implements IOC principle. DI provides objects that an object needs. Let’s say, class X is dependent on Y. So ...
Read MoreDifference Between Constructor Injection and Setter Injection in Spring
Dependency Injection is a practice to pass dependent object to other objects. Spring has two types of Dependency Injection :Constructor based Injection -When container call the constructor of the class. It should be used for mandatory dependencies.Let’s say Class X is tightly dependent on Class Y then we should use constructor based injection. Setter based Injection - It can be used by calling setter methods on your beans. It should be used for optional dependencies.Both types of injection has their own pros and cons. Below is a list of some differences −Sr. No.KeyConstructor based InjectionSetter based Injection1CircularIt doesn’t allow to ...
Read MoreHow to create bars with gap among them if there are more categories using ggplot2 in R?
When the number of categories is large in numbers for a variable and we want to create a bar plot then the display of the bar plot becomes a little ambiguous because the bars are plotted very close to each other. To make the bars clearly visible, we can reduce the width of the bars and set different colors for them to make them visually attractive.geom_bar(width=0.2,color="red")Consider the below data frame −x
Read MoreHow to create random sample based on group columns of a data.table in R?
Random sampling helps us to reduce the biasedness in the analysis. If we have data in groups then we might want to find a random sample based on groups. For example, if we have a data frame with a group variable and each group contains ten values then we might want to create a random sample where we will have two values randomly selected from each group. This can be done by using sample function inside .SDExampleConsider the below data.table −library(data.table) Group
Read MoreHow to extract values from an R data frame column that do not start and end with certain characters?
Sometimes we just want to extract the values of a data column based on initial and ending values of a column that has strings or sometimes the values of a column that has strings are recorded with some extra characters and we want to extract those values. For this purpose, we can use negation of grepl with single square brackets.ExampleConsider the below data frame −> x2 df2 head(df2, 20)Outputx2 1 Alabama 2 Alaska 3 American Samoa 4 Arizona 5 Arkansas 6 California 7 Colorado 8 Connecticut 9 Delaware 10 District of Columbia 11 Florida 12 Georgia 13 Guam 14 Hawaii ...
Read MoreHow to extract strings based on first character from a vector of strings in R?
Sometimes a vector strings have patterns and sometimes we need to make patterns from a vector of strings based on the characters. For example, we might want to extract the states name of United States of America from a vector that contains all the names. This can be done by using grepl function.ExampleConsider the below vector containing states name in USA −> US_states US_states[grepl("^A", US_states)] [1] "Alabama" "Alaska" "American Samoa" "Arizona" [5] "Arkansas" > US_states[grepl("^B", US_states)] character(0) > US_states[grepl("^C", US_states)] [1] "California" "Colorado" "Connecticut" > US_states[grepl("^D", US_states)] [1] "Delaware" "District of Columbia" > US_states[grepl("^E", US_states)] character(0) > US_states[grepl("^F", US_states)] [1] ...
Read MoreHow to find the n number of largest values in an R vector?
A vector may have thousands of values and each of them could be different or same also. It is also possible that values can be grouped or randomly selected but having few similar values. Irrespective of the values in a vector, to find some largest values we need to sort the vector in ascending order then the largest values will be selected.Examples> x1 x1 [1] -1.4447473195 3.2906645299 -0.4680055849 0.1611487482 -0.7715094280 [6] 0.4442103640 0.3702444686 0.0783124252 1.3476432299 1.0140576107 [11] -0.0968917066 0.4628821017 0.3102594626 -0.2946001275 0.1498108166 [16] -0.6002154305 0.5905382364 1.3892651534 0.1008921325 -0.6486318692 [21] -0.0562831933 -0.6887431711 0.4907512082 -0.3994662410 0.7827897030 [26] 0.5294704584 -1.3802965730 -0.6159076490 -0.0009408529 1.6182294859 ...
Read MoreHow to convert a decimal value or a vector of decimal values to fractional form in R?
A fraction form of a decimal value is the form of the value represented with division sign. For example, representing 0.5 as 1 / 2. In R, we can use fractions function of MASS package to convert a decimal value or a vector of decimal values to fractional form. To do so, we just need to pass the value in fractions function as fractions(“Decimal_value or Vector_Of_Decimal_Values”).Loading MASS package −Examples> library(MASS)Output> fractions(0.14) [1] 7/50 > fractions(1.14) [1] 57/50 > library(MASS) > fractions(0.5) [1] 1/2 > fractions(0.3) [1] 3/10 > fractions(0.31) [1] 31/100 > fractions(1.31) [1] 131/100 > fractions(2.01) [1] 201/100 > ...
Read MoreHow to create a dot plot using ggplot2 in R?
A dot plot is a type of histogram that display dots instead of bars and it is created for small data sets. In ggplot2, we have geom_dotplot function to create the dot plot but we have to pass the correct binwidth which is an argument of the geom_dotplot, so that we don’t get the warning saying “Warning: Ignoring unknown parameters: bins `stat_bindot()` using `bins = 30`. Pick better value with `binwidth`.”ExampleConsider the below data frame −> x df1 library(ggplot2)Creating the dot plot of x −> ggplot(df1, aes(x))+geom_dotplot(binwidth=0.2)OutputLet’s have a look at one more example −> y df2 ggplot(df2, aes(y))+geom_dotplot(binwidth=0.2)Output
Read MoreHow to delete different rows and columns of a matrix using a single line code in R?
Deletion or addition of rows and columns in a matrix of any size is mostly done by using single square brackets and it is also the easiest way. To delete rows and columns, we just need to use the column index or row index and if we want to delete more than one of them then we can separate them by commas by inserting them inside c as c(-1, -2). If we want to delete more than one rows or columns in a sequence then a colon can be used. Examples > M M Output ...
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