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To find the mean of a column summarized by other column names and common values in those columns in data.table object in R, we can follow the below steps −First of all, create a data.table object.Then, melt the data.table object using melt function from reshape2 package.After that, use dcast function to find the mean of a column summarized by other column names and common values in those columns.ExampleCreate the data.table objectLet’s create a data.table object as shown below −library(data.table) ID
To find the total by year column in an R data frame, we can use aggregate function with sum function.For Example, if we have a data frame called df that contains a year colmn say Year and a numerical column say Demand then we can find the total Demand by Year with the help of command given below −aggregate(df["Demand"],by=df["Year"],sum)Example 1Following snippet creates a sample data frame −Year
Problem Statement Verifying whether the string id * id + id is accepted by a given grammar using SLR parsingConsider the SLR parsing table for the GrammarE → E + TE → TT → T ∗ FT → FF → (E)F → idCheck whether the string id * id + id is accepted or not by using the SLR parsing table constructed in the example. SolutionInitially, LR Parser in state 0.Put $ at the end of the string, i.e., id * id + id $.StackInput StringReason0id ∗ ... Read More
To standardize selected columns in data.table object in R, we can follow the below steps −First of all, create a data.table object.Then, use scale function and cbind function with subsetting to standardize selected columns.ExampleCreate the data.table objectLet’s create a data.table object as shown below −library(data.table) var1
To save a matrix as CSV file using R, we can use write.matrix function of MASS package. For Example, if we have a matrix called M and we want to save it as CSV file then we can use the below mentioned command −write.matrix(M,file="Mat.csv")ExampleFollowing snippet creates a sample matrix −M
To repeat column values in R matrix by values in another column, we can follow the below steps −First of all, create a matrix.Then, use rep function along with cbind function to repeat column values in the matrix by values in another column.ExampleCreate the matrixLet’s create a matrix as shown below −x
To remove multiple columns from matrix in R by using their names, we can follow the below steps −First of all, create a matrix.Then, add names to columns of the matrix.After that, subset the matrix by deselecting the desired columns with negation and single square brackets for subsetting.ExampleCreate the matrixLet’s create a matrix as shown below −M
Deterministic Finite Automata (DFA)Deterministic means that on each input there is one and only one state to which the automata can have the transition from its current state. In deterministic finite automata, the head can move only in one direction to scan the input tape symbols. But in the case of two-way, finite automata on scanning an input symbol the head of the tape may move in right or left from its current position.There are two ways to represent Deterministic finite Automata −Transition DiagramIt is a directed graph or flow chart having states and edges. A strong path through a ... Read More
To combine two columns by ignoring missing values if exists in one column in R data frame, we can use paste function and is.na function.For Example, if we have a data frame called df that contains two columns say C1 and C2 where C2 contains some missing values then we can use the below mentioned command to combine C1 and C2 by ignoring missing values in C2 −cbind(df,Combined=paste(df[,1],replace(df[,2],is.na(df[,2]),"")))Example 1Following snippet creates a sample data frame −x1
To find the index of values in R matrix column if they occur once, we can follow the below steps −First of all, create a matrix.Then, use which function along with duplicated function and single square brackets for subsetting to find the index of values in a column if they occur once.Example 1Create the data frameLet’s create a data frame as shown below −M1