Running simulations in MATLAB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to run a simulation loop 10 times.

MATLAB

for i = 1:[1]
    disp(i)
end

Drag options to blanks, or click blank then click option'

A5

B15

C20

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using a number less than 10 will run fewer simulations.

Using a number greater than 10 will run more simulations.

The loop runs from 1 to 10 to simulate 10 iterations.

2fill in blank

medium

Complete the code to initialize the variable 'result' as an empty array before simulation.

MATLAB

[1] = [];

Drag options to blanks, or click blank then click option'

Aresult

Boutput

Csim

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name not used later in the code.

Not initializing the variable before the loop.

We initialize 'result' as an empty array to store simulation outputs.

3fill in blank

hard

Fix the error in the code to correctly store the square of i in the result array.

MATLAB

for i = 1:5
    result(i) = i[1]2;
end

Drag options to blanks, or click blank then click option'

A-

B^

C+

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using '*' multiplies by 2 instead of squaring.

Using '+' or '-' changes the value incorrectly.

The '^' operator is used for exponentiation in MATLAB to square the value.

4fill in blank

hard

Fill both blanks to create a simulation that stores the cube of each number from 1 to 4.

MATLAB

for n = 1:4
    output(n) = n[1]3;
    disp(output[2]);
end

Drag options to blanks, or click blank then click option'

A^

B*

C(n)

D[n]

Attempts:

3 left

💡 Hint

Common Mistakes

Using '*' instead of '^' for power.

Using square brackets instead of parentheses for indexing.

Use '^' to cube the number and '(n)' to access the nth element of the output array.

5fill in blank

hard

Fill all three blanks to create a simulation that stores squares of numbers greater than 2.

MATLAB

result = [];
for k = 1:5
    if k [1] 2
        result([2]) = k[3]2;
    end
end

Drag options to blanks, or click blank then click option'

A<

B>

C^

Dlength(result)+1

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' changes the condition.

Using a fixed index instead of appending to the array.

The condition checks if k is greater than 2, then stores k squared at the next index of result.

Practice

1. What is the main purpose of using a for loop in running simulations in MATLAB?

easy

A. To repeat a set of commands multiple times automatically

B. To create graphical user interfaces

C. To store data permanently on disk

D. To define new functions

Solution

1. Step 1: Understand the role of for loops

   A for loop repeats commands a fixed number of times, which is essential for running simulations step-by-step.

2. Step 2: Match the purpose to simulation needs

   Simulations require repeating calculations or processes many times to model changes over time, which for loops handle well.

3. Final Answer:

   To repeat a set of commands multiple times automatically -> Option A

4. Quick Check:

   Loop repeats commands = repeat steps [OK]

Hint: Loops repeat steps automatically, perfect for simulations [OK]

Common Mistakes:

• Confusing loops with data storage
• Thinking loops create GUIs
• Mixing loops with function definitions

2. Which of the following is the correct syntax to run a simulation loop 10 times in MATLAB?

easy

A. repeat 10 times
% simulation code
endrepeat

B. for i = 1:10
% simulation code
end

C. loop i = 1 to 10
% simulation code
endloop

D. while i < 10
% simulation code
end

Solution

1. Step 1: Recall MATLAB for loop syntax

   MATLAB uses for variable = start:end to run loops a fixed number of times.

2. Step 2: Compare options with correct syntax

   for i = 1:10 % simulation code end matches MATLAB syntax exactly; others use incorrect keywords or structures.

3. Final Answer:

   for i = 1:10 % simulation code end -> Option B

4. Quick Check:

   MATLAB loops use 'for i = start:end' [OK]

Hint: MATLAB loops use 'for i = start:end' syntax [OK]

Common Mistakes:

• Using non-MATLAB keywords like 'loop' or 'repeat'
• Confusing while with for loops
• Missing the end keyword

3. What will be the output of the following MATLAB code?

for t = 1:3
  disp(t^2)
end

medium

A. 1 4 9

B. 1 2 3

C. 2 4 6

D. Error: Undefined function

Solution

1. Step 1: Understand the loop iterations

   The loop runs with t = 1, 2, 3.

2. Step 2: Calculate the displayed values

   Each iteration displays t squared: 1^2=1, 2^2=4, 3^2=9.

3. Final Answer:

   1 4 9 -> Option A

4. Quick Check:

   Squares of 1,2,3 = 1 4 9 [OK]

Hint: Square each loop index to find output quickly [OK]

Common Mistakes:

• Printing t instead of t squared
• Confusing output with sums
• Expecting syntax errors

4. Identify the error in this MATLAB simulation code:

for i = 1:5
  result = i * 2
end
disp(result)

medium

A. Missing semicolon after result assignment

B. The loop variable 'i' is not initialized

C. No error; code runs and displays the last result

D. Variable 'result' is not defined before the loop

Solution

1. Step 1: Check variable initialization

   In MATLAB, variables can be created inside loops without prior definition.

2. Step 2: Understand loop and output behavior

   The loop runs 5 times, updating 'result' each time; after loop, 'result' holds last value (5*2=10), which is displayed.

3. Final Answer:

   No error; code runs and displays the last result -> Option C

4. Quick Check:

   Loop updates variable; last value shown [OK]

Hint: Variables inside loops update each iteration; last value remains [OK]

Common Mistakes:

• Thinking semicolons are mandatory to avoid errors
• Assuming variables must be pre-declared
• Confusing loop variable initialization

5. You want to simulate the growth of a population starting at 100, increasing by 10% each step, for 5 steps. Which MATLAB code correctly runs this simulation and stores all population values in an array pop?

hard

A. pop = zeros(5,1);
pop(1) = 100;
for i = 1:5
pop(i+1) = pop(i) * 1.1;
end

B. pop = 100;
for i = 1:5
pop = pop * 1.1;
end

C. pop = [];
for i = 1:5
pop(i) = 100 * 1.1^i;
end

D. pop = zeros(1,5);
pop(1) = 100;
for i = 2:5
pop(i) = pop(i-1) * 1.1;
end

Solution

1. Step 1: Understand the simulation requirements

   Start at 100, increase by 10% each step, store all 5 values in an array.

2. Step 2: Analyze each option for correctness

   pop = zeros(1,5); pop(1) = 100; for i = 2:5 pop(i) = pop(i-1) * 1.1; end initializes array, sets first value, then correctly updates subsequent values using previous step's value. pop = 100; for i = 1:5 pop = pop * 1.1; end overwrites single value, no array. pop = []; for i = 1:5 pop(i) = 100 * 1.1^i; end calculates powers but starts from step 1, missing initial 100 at index 1. pop = zeros(5,1); pop(1) = 100; for i = 1:5 pop(i+1) = pop(i) * 1.1; end tries to access index 6 in 5-element array, causing error.

3. Final Answer:

   pop = zeros(1,5); pop(1) = 100; for i = 2:5 pop(i) = pop(i-1) * 1.1; end -> Option D

4. Quick Check:

   Initialize array, set first value, update from previous [OK]

Hint: Initialize array, set first value, update from previous step [OK]

Common Mistakes:

• Not storing all values in an array
• Indexing beyond array size
• Overwriting single variable instead of array