Visual Basic for Applications:
Generating random numbers

How to:

In VBA, the Rnd function is used to generate random numbers. By default, Rnd generates a single-precision floating-point number greater than or equal to 0 and less than 1. Here are a few steps and examples to harness random numbers effectively:

1. Simple Random Number: To generate a basic random number, you just need to call Rnd():

   Sub GenerateRandomNumber()
       Dim randomNumber As Single
       randomNumber = Rnd() ' Random number between 0 and 1
       MsgBox randomNumber
   End Sub

2. Setting the Seed: The Randomize statement initializes the random-number generator, which can be crucial for ensuring different outcomes each time your VBA code runs:

   Sub SeedRandomNumber()
       Randomize
       Dim randomNumber As Single
       randomNumber = Rnd()
       MsgBox randomNumber
   End Sub

3. Generating Numbers in a Range: Often, you’ll want a random number within a specific range. Here’s how to generate a number between 1 and 100:

   Sub RandomNumberInRange()
       Randomize
       Dim randomNumber As Integer
       randomNumber = Int((100 * Rnd()) + 1) ' Random number between 1 and 100
       MsgBox randomNumber
   End Sub

Sample Output:

After running RandomNumberInRange, you might see a message box displaying a number like 45.

Deep Dive:

The Rnd function in VBA, while easy to use, actually generates pseudo-random numbers based on a deterministic algorithm. This means the sequences of numbers it produces are not truly random but can often suffice for common tasks needing stochastic processes.

Historically, the random number generation capability in VBA dates back to early versions of Basic, adapting over time to include features like Randomize to improve the randomness by seeding the algorithm with a starting point. However, for applications requiring high levels of randomness such as secure cryptographic operations, VBA’s Rnd might not be the best tool. Alternatives in more robust programming environments or languages designed with cryptography in mind, like Python’s secrets module or Java’s SecureRandom, should be considered.

Despite its limitations, the simplicity and accessibility of generating random numbers in VBA continue to make it a valuable tool for a wide range of lighter applications, simulation work, and educational purposes.