Random

Programming is usually very predictable. The same things happen at the same time, and if that part of the program is in a loop, those things will happen over and over again. But what if you don’t want to know what’s going to happen? What if you’re using a Magic 8 ball app, or if you’re programming a Clapping Monkey Bot to wait a random amount of time before clapping its hands? In those cases, you will probably want to use randomization.

There are two different ways to create a random value:

int value = random(max);

or

int value = random(min, max);

These are the differences between the two:

• random(max) will pick a value from 0 up to, but not including, the number you put as the maximum value. For example, if you have a maximum value of 10, the program will pick any number from 0 to 9.
• random(min, max) will pick a value between your minimum number and up to, but not including, your maximum number. For example, if you have a minimum value of 5 and a maximum value of 10, the program will pick any number from 5 to 9.

Check out the example code to see how random() can be used with if and else if statements. This code has an output for every number that can be selected.

int choice;
 
void setup() {
 Serial.begin(9600); // start the Serial monitor
}
 
void loop() {

// pick a random number from 0-4 (not including 4)
 choice = random(4); 
 // print out a message depending on the random number
 if(choice == 0)
 {
   Serial.println("Hi");
 }
 else if (choice == 1)
 {
   Serial.println("Bye");
 }
 else if (choice == 2)
 {
   Serial.println("Good morning");
 }
 else if (choice == 3)
 {
   Serial.println("Good night");
 }
 
 delay(500); // slow it down to watch what is happening
}

So what’s going on with the code?

The program is designed to randomly pick a number between 0 and 4 (but not including 4!). Once the number is picked, the program uses if and else if statements to print a message in the serial monitor. After about half a second, the program will run again!

This is what the serial monitor’s screen could look like after running the program:

Good night

Bye

Bye

Good morning

Good morning

Hi

Hi

Good morning

Good night

Bye

Hi

Bye

Hi

Good morning

Good night

Still not sure about randomization? Watch the video!