Programming Articles - Page 896 of 3363

To convert list with varying number of elements into a data frame in R, we can use stri_list2matrix function of stringi package along with as.data.frame function.For Example, if we have a list called LIST that contains varying number of elements then we can convert it into a data frame by using the below mentioned command −as.data.frame(t(stri_list2matrix(LIST)))Example 1Following snippet creates a sample list −List1

To combine two rows in R matrix by addition, we can follow the below steps −First of all, create a matrix.Then, using plus sign (+) to add two rows and store the addition in one of the rows.After that, remove the row that is not required by subsetting with single square brackets.ExampleCreate the matrixLet’s create a matrix as shown below −M

To convert alphabets to numbers in data.table object in R, we can follow the below steps −First of all, create a data.table object.Then, use mutate_each function of dplyr package along with chartr function to convert alphabets to numbers.ExampleCreate the data.table objectLet’s create a data.table object as shown below −library(data.table) v1

To find the percentage of values that lie within a range in R data frame column, we can follow the below steps −First of all, create a data frame.Then, use sum function along with extreme values for range and length function to find the percentage of values that lie within that range.ExampleCreate the data frameLet’s create a data frame as shown below −Var

To find the frequency of each value in an R data frame, we can use table function along with unlist function.For Example, if we have a data frame called df and we want to find the frequency of each value in df then we can use the below command −table(unlist(df))Example 1Following snippet creates a sample data frame −x1

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

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 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 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