Introduction Objectives

• Think computationally
• Use logic
• Solve problems
• Instruct computer to do something

Block programming and R implementation

Learning programming and coding might seem daunting, but it really boils down to being able to define specific steps needed to solve a problem or accomplish a task. This involves using logical thinking and problem solving, including sequencing and conditional logic, to assemble a step-by-step solution. We’ll use block programming to explore this.

Block programming is a method of learning the principles of coding via a visual interface. Learners drag and drop blocks of instructions into the order they want them to be executed, all without having to learn a programming language.
It will get you familiar with thinking computationally before learning a scripting language such as R.

For example, the following instructions can be put together into a program:

1. let my variable refer to a real integer between 1 and 20
2. let if condition test whether my_variable is less than 10
3. if my variable satisfies the if condition, add two to my variable
4. print my variable
5. if my variable does not satisfy the if condition, set my variable to 100
6. print my variable

The following is a script in the R programming language that implements the instructions above.

my_variable <- sample(1:20, 1)

if (my_variable < 10) {
  my_variable <- my_variable + 2
  print(my_variable)
} else {
  my_variable <- 100
  print(my_variable)
}

If you understand the instructions above, then you know what the R code is accomplishing even though you can’t read the R language. However, you can probably deduce what a lot of it is doing!

• What do you think the combination of characters <- means? What about the pattern {...}?

• Which step is implemented by the if (...) {...} block?

• What is the role of my_variable?

Block programming Exercise 1

Go to the block programming platform Scratch and use the instructions above to assemble a program that prints a number.

For fun, see if you can create a program that makes the cat walk across the screen!

Block programming Exercise 2

Complete the following instructions to test whether a given integer is even or odd. Assume you can use a pre-existing capability to round any number to its nearest integer, as well as the arithmetic operators * and /.

1. let i refer to a given integer
2. if i is less than zero, let i refer to -1 * i
   …

Block programming Exercise 3

One common task in programming is to do a series of steps many times, which is called a loop in coding.
In the Scratch platform, create a program that calculates the square root of each number from 1-20, and if the result is an integer, print the square root.

If you need to catch-up before a section of code will work, just squish it's 🍅 to copy code above it into your clipboard. Then paste into your interpreter's console, run, and you'll be ready to start in on that section. Code copied by both 🍅 and 📋 will also appear below, where you can edit first, and then copy, paste, and run again.

# Nothing here yet!