Type conversion functions in MATLAB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the double() function do in MATLAB?

The double() function converts a variable to double-precision floating-point format, which is MATLAB's default numeric type.

beginner

How do you convert a number to an integer type in MATLAB?

You can use functions like int8(), int16(), int32(), or int64() to convert a number to signed integer types of different sizes.

beginner

What is the purpose of the char() function in MATLAB?

The char() function converts numeric values to their corresponding ASCII characters or converts other data types to character arrays.

intermediate

Explain the difference between single() and double() in MATLAB.

single() converts data to single-precision floating-point format, which uses less memory but less precision than double(), which is double-precision and the default numeric type.

intermediate

What happens if you convert a floating-point number to an integer type in MATLAB?

When converting a floating-point number to an integer type, MATLAB rounds the number towards zero (truncates the decimal part) and converts it to the specified integer type.

Which MATLAB function converts a variable to a character array?

A int32()

B double()

C char()

D single()

The char() function converts data to character arrays.

What type does double() convert data into?

A Double-precision floating-point

B Single-precision floating-point

C Integer

D Character

double() converts data to double-precision floating-point format.

If you convert 3.7 to an integer type using int32(), what is the result?

A Error

B 4

C 3.7

D 3

MATLAB truncates the decimal part, so 3.7 becomes 3.

Which function would you use to convert data to single-precision floating-point?

A char()

B single()

C int16()

D double()

single() converts data to single-precision floating-point format.

What happens if you convert a character array to double using double()?

A It converts characters to their ASCII numeric codes

B It causes an error

C It converts characters to integers

D It converts characters to single precision

double() converts characters to their ASCII numeric codes.

Describe how MATLAB converts floating-point numbers to integer types using type conversion functions.

Think about what happens to the decimal part when converting.

Explain the difference between single() and double() conversion functions in MATLAB.

Consider precision and memory usage.

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