Type conversion functions in MATLAB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to convert the variable x to a double precision number.

MATLAB

y = [1](x);

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

Alogical

Bint32

Cchar

Ddouble

Attempts:

3 left

💡 Hint

Common Mistakes

Using int32 instead of double changes the type incorrectly.

Using char converts to characters, not numbers.

The double function converts the input to double precision.

2fill in blank

medium

Complete the code to convert the string s to a numeric value.

MATLAB

num = [1](s);

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

Aint8

Bchar

Cstr2double

Dlogical

Attempts:

3 left

💡 Hint

Common Mistakes

Using char converts to characters, not numbers.

Using int8 converts to integer but not from string.

The str2double function converts a string to a double number.

3fill in blank

hard

Fix the error in the code to convert the number n to a character.

MATLAB

c = [1](n);

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

Achar

Bstr2double

Cint32

Ddouble

Attempts:

3 left

💡 Hint

Common Mistakes

Using double converts to double precision, not characters.

Using str2double converts strings to numbers, not numbers to characters.

The char function converts numeric values to characters.

4fill in blank

hard

Fill both blanks to convert the variable a to an integer and then to a logical value.

MATLAB

b = [1](a);
c = [2](b);

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

Aint32

Bdouble

Clogical

Dchar

Attempts:

3 left

💡 Hint

Common Mistakes

Reversing the order of conversions.

Using double instead of int32 for integer conversion.

First convert a to integer with int32, then convert that integer to logical with logical.

5fill in blank

hard

Fill all three blanks to convert the string str to a double, then to an integer, and finally to a character.

MATLAB

num = [1](str);
intVal = [2](num);
charVal = [3](intVal);

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

Astr2double

Bint32

Cchar

Dlogical

Attempts:

3 left

💡 Hint

Common Mistakes

Skipping the double conversion step.

Using logical instead of char at the end.

Convert string to double with str2double, then to integer with int32, and finally to character with char.

Practice

1. Which MATLAB function converts a string representing a number into a numeric double type?

easy

A. str2double

B. double

C. int32

D. char

Solution

1. Step 1: Understand the input and output types

   The input is a string representing a number, and the output should be a numeric double type.

2. Step 2: Identify the correct conversion function

   str2double converts strings to double numbers, while double converts numeric types to double, int32 converts to 32-bit integers, and char converts numbers to characters.

3. Final Answer:

   str2double -> Option A

4. Quick Check:

   String to double = str2double [OK]

Hint: Use str2double for string to number conversion [OK]

Common Mistakes:

• Using double on a string causes error
• Using int32 converts to integer, not double
• Using char converts to characters, not numbers

2. Which of the following is the correct syntax to convert a numeric variable x to a 32-bit integer in MATLAB?

easy

A. convertToInt32(x)

B. int(x, 32)

C. int32(x)

D. toInt32(x)

Solution

1. Step 1: Recall MATLAB's type conversion syntax

   MATLAB uses functions named after the target type, like int32, called with parentheses around the variable.

2. Step 2: Check each option's syntax

   Only int32(x) is valid MATLAB syntax. The others are not MATLAB functions or use incorrect syntax.

3. Final Answer:

   int32(x) -> Option C

4. Quick Check:

   Correct syntax for int32 conversion = int32(x) [OK]

Hint: Use function name with parentheses for conversion [OK]

Common Mistakes:

• Using non-existent functions like convertToInt32
• Incorrect function call syntax
• Confusing with other language syntax

3. What is the output of the following MATLAB code?

x = '123.45';
y = str2double(x);
z = int32(y);
disp(z);

medium

A. 123.45

B. '123.45'

C. Error

D. 123

Solution

1. Step 1: Convert string to double

   str2double('123.45') converts the string to numeric double 123.45.

2. Step 2: Convert double to int32

   int32(123.45) converts the double to integer by truncating the decimal part, resulting in 123.

3. Final Answer:

   123 -> Option D

4. Quick Check:

   str2double + int32 truncates decimals = 123 [OK]

Hint: int32 truncates decimals after str2double [OK]

Common Mistakes:

• Expecting int32 to round instead of truncate
• Thinking str2double returns string
• Confusing output with original string

4. Identify the error in this MATLAB code snippet:

x = 65;
y = str2double(x);
disp(y);

medium

A. str2double cannot convert numeric input

B. x should be a string for str2double

C. Missing semicolon after disp(y)

D. disp cannot display numeric values

Solution

1. Step 1: Check input type for str2double

   str2double expects a string input, but x is numeric (65).

2. Step 2: Identify the cause of error

   Passing numeric x to str2double causes unexpected behavior or error because it is not a string.

3. Final Answer:

   x should be a string for str2double -> Option B

4. Quick Check:

   str2double needs string input [OK]

Hint: str2double requires string input, not numeric [OK]

Common Mistakes:

• Passing numeric directly to str2double
• Thinking disp needs semicolon
• Believing disp can't show numbers

5. You have a cell array of strings representing numbers: data = {'10', '20.5', '30', '40.7'}. Which MATLAB code correctly converts all elements to a numeric array of doubles?

hard

A. numArray = cellfun(@str2double, data);

B. numArray = double(data);

C. numArray = int32(data);

D. numArray = str2double(data);

Solution

1. Step 1: Understand data type and conversion needed

   data is a cell array of strings; we want a numeric double array.

2. Step 2: Use cellfun with str2double

   cellfun(@str2double, data) applies str2double to each cell element, converting strings to doubles.

3. Step 3: Check other options

   double(data) and int32(data) do not work on cell arrays directly; str2double(data) expects a string, not a cell array.

4. Final Answer:

   numArray = cellfun(@str2double, data); -> Option A

5. Quick Check:

   Use cellfun with str2double for cell string arrays [OK]

Hint: Use cellfun(@str2double, cellArray) for cell string to numbers [OK]

Common Mistakes:

• Trying double or int32 on cell arrays directly
• Using str2double on cell array without cellfun
• Not converting strings inside cells individually