*68*

The triangular distribution is a continuous probability distribution with a probability density function shaped like a triangle.

It is defined by three values:

- The minimum value
*a* - The maximum value
*b* - The peak value
*c*

To calculate probabilities for the triangular distribution in R we can use the **ptri(**) function from the **EnvStats** package, which uses the following syntax:

**ptri(q, min = 0, max = 1, mode = 1/2)**

where:

**q**: Quantile of interest**min**: The minimum value of the distribution**max**: The maximum value of the distribution**mode**: The peak value of the distribution

The following examples show how to use this function in practice in R.

**Example 1: Calculating Probability Less Than Some Value**

Suppose a restaurant estimates that their total sales for the upcoming week will be a minimum of $10,000, a maximum of $30,000, and most likely $25,000.

**What is the probability that the restaurant makes less than $20,000 total sales?**

We can use the following code to calculate this probability:

library(EnvStats) #calculate probability ptri(q = 20000, min = 10000, max = 30000, mode = 25000) [1] 0.3333333

The probability that the restaurant makes less than $20,000 total sales is **.333**.

**Example 2: ****Calculating Probability Greater Than Some Value**

Suppose a shop estimates that the number of customers that will enter in a given week will be a minimum of 500, a maximum of 2,000, and most likely 1,200.

**What is the probability that more than 1,500 customers enter the shop in a given week?**

We can use the following code to calculate this probability:

library(EnvStats) #calculate probability 1 - ptri(q = 1500, min = 500, max = 2000, mode = 1200) [1] 0.2083333

The probability that more than 1,500 customers enter the shop is about **.208.**

**Note**: You can find the complete documentation for the **ptri()** function here.

**Additional Resources**

The following tutorials explain how to work with other probability distributions in R:

How to Use the Normal Distribution in R

How to Use the Binomial Distribution in R

How to Use the Poisson Distribution in R

How to Use the Multinomial Distribution in R