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A regular expression is a special sequence of characters that helps you match or find other strings or sets of strings, using a specialized syntax held in a pattern. They can be used to search, edit, or manipulate text and data. Java provides the java.util.regex package for pattern matching with regular expressions.Matcher classA Matcher object is the engine that interprets the pattern and performs match operations against an input string. Like the Pattern class, Matcher defines no public constructors. You obtain a Matcher object by invoking the matcher() method on a Pattern object.The Instances of this class are not safe ... Read More
The String class of the java.lang package represents set of characters. All string literals in Java programs, such as "abc", are implemented as instances of this class. A string index is an integer representing the position of each character in the string starting from zero.A substring is a part/segment of a string. You can identify a substring of a string using the substring() method of the String class. This method have two variants −substring(int beginIndex)This method accepts an integer value representing an index in the current string and returns the substring starting from the given index to the end of ... Read More
If we have a character column that means we are more likely to have duplicated values in that column hence finding the mean of numerical columns based on the values in character column cannot be done directly. For this purpose, we can use aggregate function as shown in the below examples.Example1Consider the below data frame − Live Demoset.seed(214) x1
Given an Integer N the task is to replace all the 0’s that appear in the number with ‘5’. However, the number with leading ‘0’ cannot be replaced with ‘5’ as it remains unchanged. For example, Input-1 −N = 1007Output −1557Explanation − The given number has 2 zeros which when replaced by ‘5’ results in the output as 1557.Input-2 −N = 00105Output −155Explanation − Since the given number starts with the leading ‘0’ which can be ignored and the output after replacing the 0 in the middle with ‘5’ results the output as 155.Approach to solve this problemTo replace all ... Read More
Depending on our objective, a matrix rows might be needed to converted into a list that means each row will be an element of the list. This can be done by using the function as.list but firstly we need to convert the matrix into data frame after transposing. For example, if we have a matrix called M then it’s rows will be converted to a list using the command writtem below −as.list(data.frame(t(M)))Example1 Live DemoM1
To create the bins for a continuous vector, we can use cut function and store the bins in a data frame along with the original vector. The values in the cut function must be passed based on the range of the vector values, otherwise, there will be NA’s in the bin values. For example, if we have a vector that contains 0.55 and we do not use 0 in the cut function then the first bin will be NA. Check out the below examples to understand how to properly do it.Example1 Live Demox1
Sometimes numerical values are recorded as character values and we need to convert them to numeric type before starting our analysis. This is also possible for a whole data frame in R. Therefore, we can use sapply function to convert the columns of the data frame to numeric type and save the output in a data frame by reading it with as.data.frame.Example1Consider the below data frame − Live Demox
The boxplot in base R is covered with a box and that box is called a frame. We can get rid of that frame by using frame argument while creating the boxplot. For example, if we have a vector called x and we want to create the boxplot without frame then it can be done by using the command boxplot(x,frame=F). This will remove all the sides of the boxplot except the Y−axis labels because this will help us to understand the distribution of the variable.Example Live Demox
If there are missing values in a vector then the plot of such vector will not have all the values, only the non−missing values will be shown. If we want to create the plot by adding the missing values in the plot then we need to define the X−axis for the length of the vector and the Y−axis with the actual vector using cbind but missing values will be omitted as shown in the below example.Example Live Demox
Whenever we print any vector then the left-hand side of the R window shows indexing, even if we have one value in the vector the index will be there. For example, if we print a vector that has value equal to 2 then the print output will be [1] 2, here [1] represents the index. If we want to print the vector without index then cat function can be used as shown in the below examples.Example1 Live Demox1