Free MATLAB Functions and Flow Control Questions and Answers — Questions and Answers
Question 1: A function `calculateArea` is defined as follows:
```matlab
function area = calculateArea(width, height)
if nargin == 1
% Assume a square if only one input is given
height = width;
end
area = width * height;
end
```
What is the output of the command `calculateArea(5)`?
- 25 (Correct answer)
- Error: Not enough input arguments.
- 0
- 5
Correct answer: 25
The function is called with one argument, so the special variable `nargin` returns 1. The `if` condition evaluates to true, causing the `height` variable to be assigned the value of `width` (which is 5). The function then calculates `area = 5 * 5`, returning 25.
Question 2: A script `mainScript.m` contains the following code:
```matlab
% mainScript.m
value = 10;
modifyValue(value);
disp(value);
```
The function `modifyValue` is defined in a separate file `modifyValue.m`:
```matlab
function modifyValue(inputArg)
inputArg = inputArg + 5;
end
```
Assuming both files are in the current directory, what is displayed in the Command Window when `mainScript` is run?
- 15
- 10 (Correct answer)
- An error is thrown because `value` is not returned.
- 5
Correct answer: 10
MATLAB passes arguments to functions by value. This means that when `value` is passed to `modifyValue`, a local copy of the variable is created within the function's workspace named `inputArg`. Modifying `inputArg` inside the function does not affect the original `value` variable in the script's (base) workspace. Therefore, the value of `value` remains 10.
Question 3: After executing the following code, what is the final value of `x`?
```matlab
x = 1;
n = 10;
while x <= n
x = x * 2;
n = n - 1;
end
```
Correct answer: 8
The loop executes as follows:
- Pass 1: `x=1`, `n=10`. Condition `1<=10` is true. `x` becomes `2`, `n` becomes `9`.
- Pass 2: `x=2`, `n=9`. Condition `2<=9` is true. `x` becomes `4`, `n` becomes `8`.
- Pass 3: `x=4`, `n=8`. Condition `4<=8` is true. `x` becomes `8`, `n` becomes `7`.
- Pass 4: `x=8`, `n=7`. Condition `8<=7` is false. The loop terminates.
The final value of `x` is 8.
Question 4: Consider the following function `countCalls`:
```matlab
function currentCount = countCalls()
persistent callCounter;
if isempty(callCounter)
callCounter = 1;
else
callCounter = callCounter + 1;
end
currentCount = callCounter;
end
```
If the following commands are executed sequentially in the Command Window, what is the final value of `c`?
```matlab
countCalls();
countCalls();
c = countCalls();
```
- 1
- 2
- An error occurs because `callCounter` is not initialized.
- 3 (Correct answer)
Correct answer: 3
A `persistent` variable is local to a function but retains its value in memory between calls to that function. The first call initializes `callCounter` to 1. The second call increments it to 2. The third call increments it to 3, and this final value is assigned to the output variable `c`.
Question 5: A programmer needs to search a numeric vector `V` for the first element greater than 100 and store its index. Which code snippet correctly and most efficiently accomplishes this?
- ```matlab
targetIndex = -1;
for k = 1:length(V)
if V(k) > 100
targetIndex = k;
break;
end
end
``` (Correct answer)
- ```matlab
targetIndex = -1;
for k = 1:length(V)
if V(k) > 100
targetIndex = k;
end
end
```
- ```matlab
targetIndex = -1;
for k = 1:length(V)
if V(k) <= 100
continue;
end
targetIndex = k;
end
```
- ```matlab
targetIndex = find(V > 100, 1, 'first');
continue;
```
Correct answer: ```matlab
targetIndex = -1;
for k = 1:length(V)
if V(k) > 100
targetIndex = k;
break;
end
end
```
The `break` statement immediately terminates the `for` loop as soon as the condition `V(k) > 100` is met. This is the most efficient approach because it stops unnecessary iterations once the first matching element is found. The second option finds the *last* such element, not the first. The third option also finds the *last* such element. The fourth option is syntactically incorrect as `continue` cannot be used outside of a loop.
Question 6: What is the value of `result` after this code is executed?
```matlab
value = 'medium';
switch value
case {'low', 'minimum'}
result = 1;
case 'medium'
result = 2;
case 'high'
result = 3;
otherwise
result = 0;
end
```
- 1
- 2 (Correct answer)
- 0
- An error occurs because 'medium' is a string.
Correct answer: 2
The `switch` statement compares the `switch_expression` (`value`) to each `case`. The variable `value` contains the character vector 'medium', which exactly matches the second `case 'medium'`. MATLAB executes the statement associated with that case, `result = 2;`, and then exits the switch block.
