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Articles by Nizamuddin Siddiqui
Page 23 of 196
How to combine two rows in data.table object in R by addition?
To combine two rows in data.table object in R by addition, we can follow the below steps −First of all, create a data.table object.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 data.table objectLet’s create a data.table object as shown below: −library(data.table) x
Read MoreHow to find the groupwise mean and groupwise sum at the same time in an R data frame?
To find the groupwise mean and groupwise sum at the same time, we can first convert the data frame into a data.table object and then apply the sum function and mean function for data.table object groups as shown in the below examples.Example 1Following snippet creates a sample data frame −Group
Read MoreHow to minus every element of a vector with every element of another vector in R?
To minus every element of a vector with every element of another vector, we can use outer function by defining the subtraction sign.For example, if we have two vectors say x and y and we want to minus every element in x from every element in y then we can use the below mentioned command −outer(x,y,`-`)Example 1Following snippet creates a sample vector −x1
Read MoreHow to create a column of total in data frames stored in R list?
To create a column of total in data frames stored in R list, we can follow the below steps −First of all, create a list of data frames.Then, use lapply function to create a column of total in data frames stored in the list.ExampleCreate the list of data framesUsing data.frame function to create data frames and list function to create the list of those data frames −df1
Read MoreHow to change the name of data frames stored in an R list?
To change the name of data frames stored in an R list, we can follow the below steps −First of all, create a list of data frames.Then, use names function to change the name of data frames.ExampleCreate the list of data framesUsing data.frame function to create data frames and list function to create the list of those data frames −df1
Read MoreHow to find all combinations of a vector elements without space in R?
When we want to find the combinations of a vector elements, we can use combn function with size of the combination say 2 for pairs but the result gives space between the values. If we do not want to get the combinations with space then combn function will be used with paste function by collapsing the space as shown in the below examples.Check out the below examples to understand how it can be done.Example 1To find all combinations of a vector elements without space, use the snippet given below −x1
Read MoreHow to find the cumulative sum for each row in an R data frame?
To find the cumulative sum for each row in an R data frame, we would need to read the data frame as a data.table object and then Reduce function will be used with accumulate argument.For Example, if we have a data frame called df and we want to find the cumulative sum for each row in df then we can use the below mentioned command −setDT(df)[,names(df):=Reduce("+",df,accumulate=TRUE)]Example 1Following snippet creates a sample data frame −x1
Read MoreHow to find the frequency of particular value in rows of an R data frame?
To find the frequency of particular value in rows of an R data frame, we can use mutate function of dplyr package along with rowSums function.For example, if we have a data frame called df then we can find the number of 5’s in each row of df by using the below command −df%>%mutate(Number_of_Fives=rowSums(.==1))Example 1Following snippet creates a sample data frame −x1
Read MoreHow to find the column maximum if some columns are categorical in R data frame?
To find the column maximum 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 maximum if some columns are categorical.Example 1Create the data frameLet’s create a data frame as shown below −Group
Read MoreHow to replace numbers written in words with numbers in an R data frame column?
To replace numbers written in words with numbers in an R data frame column, we can use within function.For example, if we have a data frame called df that contains a column say X having numbers from 1 to 5 written in words then we can convert them into numbers by using the below command −within(df,X
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