To select data.table object columns based on their class in R, we can follow the below steps −First of all, create a data.table object.Then, use str function to check the structure of the object.After that, use select_if function from dplyr package to select the columns based on their class.Example 1Create the data.table objectLet’s create a data.table object as shown below −library(data.table) x1

To create a replacement column with multiple conditions and NA in data.table object in R, we can follow the below steps −First of all, create a data.table object.Then, use nested ifelse function to create a replacement column with multiple conditions.ExampleCreate the data.table objectLet’s create a data.table object as shown below −library(data.table) x

To find the sum of rows of a column based on multiple columns in R’s data.table object, we can follow the below steps−First of all, create a data.table object.Then, use aggregate function to find the sum of rows of a column based on multiple columns.ExampleCreate the data.table objectLet’s create a data.table object as shown below −library(data.table) F1

To remove dollar sign in data.table object in R, we can follow the below steps −First of all, create a data.table object.Then, use gsub function along with lapply function to remove dollar sign.ExampleCreate the data.table objectLet’s create a data.table object as shown below −library(data.table) Sale_Price

To multiply vector values in sequence with data.table object columns in R, we can follow the below steps:−First of all, create a data.table.Then, create a vector.After that, use t function for transpose and multiplication sign * to multiply vector values in sequence with data.table object columns.Example 1Create the data.table objectLet’s create a data.table object as shown below −library(data.table) var1

To find the column totals if some columns are categorical in R data frame, we can follow the below steps −First of all, create a data frame.Then, use numcolwise function from plyr package to find the column totals if some columns are categorical.Example 1Create the data frameLet’s create a data frame as shown below −Grp

To add rows in an R data frame, we can follow the below steps −First of all, create a data frame.Then, use rbind function and the vectors that will be added as rows to the data frame.ExampleCreate the data frameLet’s create a data frame as shown below −x

To create a column of first non-zero value in each row of a data.table object in R, we can follow the below steps −First of all, create a data.table object with some zero values.Then, use apply function and a custom function to find the first non-zero in each row of the data.table object.ExampleCreate the data.table objectLet’s create a data.table object as shown below −library(data.table) v1

To find the percent 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 along with ncol function to find the percent of zeros in each row of the data frame.ExampleCreate the data frameLet’s create a data frame as shown below −x

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