# How do I count aggregates in R?

## How do I count aggregates in R?

In order to use the aggregate function for mean in R, you will need to specify the numerical variable on the first argument, the categorical (as a list) on the second and the function to be applied (in this case mean ) on the third. An alternative is to specify a formula of the form: numerical ~ categorical .

### How do I count unique characters in R?

Answers

- We can use str_count library(stringr) sum(!!str_count(str1, letters)) #[1] 3.
- You can use strsplit and sapply functions sapply(strsplit(str1, ” “), length)

**How do I count unique values in a column in R?**

To find unique values in a column in a data frame, use the unique() function in R. In Exploratory Data Analysis, the unique() function is crucial since it detects and eliminates duplicate values in the data.

**What are aggregates in R?**

Aggregate() Function in R Splits the data into subsets, computes summary statistics for each subsets and returns the result in a group by form. Aggregate function in R is similar to group by in SQL. Aggregate() function is useful in performing all the aggregate operations like sum,count,mean, minimum and Maximum.

## How do you count unique characters in a string?

Given a string, find the all distinct (or non-repeating characters) in it….Traverse the input string str and do following for every character c = str[i].

- Increment count[x].
- If count[x] is 1, then store index of x in index[x], i.e., index[x] = i.
- If count[x] is 2, then remove x from index[], i.e., index[x] = n.

### What is the difference between unique and distinct in R?

distinct returns an ordered list, whereas unique returns the row number of the first occurrence of each unique element. Overall, both functions return the unique row elements based on the combined set of columns chosen.

**How to count unique values in R?**

A completely different approach for the counting of unique values in R is provided by the aggregate function in combination with the data.frame, the list, and the length functions. Have a look at the following R code: As you can see, we produced a similar output as in Example 2, but this time based on a completely different R syntax.

**How to aggregate data in R?**

Another useful function to aggregate the variable is sum (). You can check which leagues have the more homeruns. Spread in the data is computed with the standard deviation or sd () in R.

## How to count observations by group in R?

Count observations by group is always a good idea. With R, you can aggregate the the number of occurence with n (). For instance, the code below computes the number of years played by each player. You can select the first, last or nth position of a group. For instance, you can find the first and last year of each player.

### How to count unique values by group in Python using dplyr?

We first have to install and load the dplyr package, if we want to use the corresponding functions: Now, we can apply the group_by and summarise functions of the dplyr package to return a tibble showing the group counts of our data: Another alternative for counting unique values by group is provided by the data.table package.