Server Side Programming Articles - Page 745 of 2650

To remove rows in data.table object in R that contains a specific number, we can follow the below steps −First of all, create a data.table object.Then, use single square subsetting with apply function to remove rows that contains a specific number.ExampleCreate the data.table objectLet’s create a data.table object as shown below: −library(data.table) x

To change the sign of even number rows in R matrix, we can follow the below steps −First of all, create a matrix.Then, use vector multiplication with 1 and minus 1 to change the sign of even number rows.ExampleCreate the matrixLet’s create a matrix as shown below −M

To add a value to a particular matrix element in R, we can use subsetting for the particular value with single square brackets.For Example, if we have a matrix called M and we want to add 10 to the fifth value in second column then can use the below mentioned command −M[5,2]

To multiply row values in a matrix having multiple rows with single row matrix in R, we can follow the below steps −First of all, create a matrix with multiple rows and a matrix with single row.Then, use mapply function to multiply row values in those matrices.ExampleCreate the first matrixLet’s create a matrix as shown below −M1

To subset a data.table object in R by ignoring a value in one of the columns, we can follow the below steps −First of all, create a data.table object.Then, use single square brackets to subset the data.table object by ignoring a value in one of the columns.ExampleCreate the data.table objectLet’s create a data.table object as shown below −library(data.table) x

To find the percentage of each category in a data.table object in R, we can follow the below steps −First of all, create a data.table object.Then, use summarise function of dplyr package after grouping along with n and nrow.ExampleCreate the data.table objectLet’s create a data.table object as shown below −library(data.table) Factor

To find the number of zeros in each row of an R data frame, we can follow the below steps −First of all, create a data frame.Then, use rowSums function to find the number of zeros in each row of the data frame.ExampleCreate the data frameLet’s create a data frame as shown below −x

To find the number of columns where all row values are equal in R matrix, we can follow the below steps −First of all, create a matrix.Then, use sum function along with length and apply function to find the number of columns where all row values are equal.Example 1Create the matrixLet’s create a matrix as shown below −M1

If we have a data frame that contains columns having names with some commong strings then we might want to find those column names. For this purpose, we can use grepl function for subsetting along with colnames function.Check out the Examples given below to understand how it can be done.Example 1Following snippet creates a sample data frame −Students_Score

To create pivot table with sum for data stored in R data frame, we can follow the below steps −First of all, create a data frame with two categorical and one numerical column.Then, use dcast function from reshape2 package to create pivot table for the data stored in data frame.ExampleCreate the data frameLet’s create a data frame as shown below −Group