FREE MATLAB Functions and Flow Control 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)`?

Accepted Answer

25

Answer

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?

Accepted Answer

10

Answer

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
```

Accepted Answer

8

Answer

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();
```

Accepted Answer

3

Answer

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?

Accepted Answer

```matlab
targetIndex = -1;
for k = 1:length(V)
    if V(k) > 100
        targetIndex = k;
        break;
    end
end
```

Answer

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.

MATLAB - MATLAB Technical Computing Practice Test

MATLAB - MATLAB Technical Computing Practice Test

FREE MATLAB Functions and Flow Control Questions and Answers