Numeric types (double, single, integer) in MATLAB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the default numeric type in MATLAB?

The default numeric type in MATLAB is double precision floating-point.

beginner

How do you create a single precision number in MATLAB?

Use the single() function to convert a number to single precision, e.g., a = single(3.14);.

beginner

What is the difference between integer types and floating-point types in MATLAB?

Integer types store whole numbers without fractions, while floating-point types (double, single) can store numbers with decimals.

intermediate

Name three integer types available in MATLAB.

Three integer types in MATLAB are int8, int16, and int32. There are also unsigned versions like uint8.

intermediate

What happens if you assign a decimal number to an integer type variable in MATLAB?

MATLAB truncates the decimal number toward zero and stores only the integer part, discarding the fractional part.

Which numeric type is used by default when you write x = 5; in MATLAB?

A double

B single

C int32

D uint8

By default, MATLAB stores numbers as double precision floating-point.

How do you convert a number to single precision in MATLAB?

A Use <code>int8()</code>

B Use <code>uint16()</code>

C Use <code>double()</code>

D Use <code>single()</code>

The single() function converts numbers to single precision.

Which of these is NOT an integer type in MATLAB?

A single

B int16

C uint8

D int32

single is a floating-point type, not an integer type.

What happens if you assign 3.7 to an int8 variable?

A It stores 3.7

B It stores 4

C It stores 3

D It causes an error

MATLAB truncates the decimal part and stores only the integer part.

Which numeric type uses the least memory in MATLAB?

A double

B int8

C single

D int32

int8 uses 1 byte, which is less than single (4 bytes) and double (8 bytes).

Explain the differences between double, single, and integer numeric types in MATLAB.

Think about precision, memory size, and value types.

Describe what happens when you assign a decimal number to an integer variable in MATLAB.

Consider how MATLAB handles fractional parts for integers.

Practice

1. Which numeric type is the default in MATLAB when you create a number like 5 without specifying its type?

easy

A. single

B. uint8

C. int32

D. double

Solution

1. Step 1: Understand MATLAB default numeric type

   By default, MATLAB stores numbers as double precision floating-point values.

2. Step 2: Check the given number type

   The number 5 without any type specification is stored as double.

3. Final Answer:

   double -> Option D

4. Quick Check:

   Default numeric type = double [OK]

Hint: Remember: MATLAB defaults to double unless specified [OK]

Common Mistakes:

• Thinking single is default
• Confusing integer types as default
• Assuming uint8 is default

2. Which of the following is the correct way to create a single precision number with value 3.14 in MATLAB?

easy

A. x = single(3.14);

B. x = double(3.14);

C. x = int32(3.14);

D. x = single '3.14';

Solution

1. Step 1: Identify correct syntax for single precision

   Use the function single() with a numeric argument to create a single precision number.

2. Step 2: Check each option

   x = single(3.14); uses single(3.14) which is correct syntax. x = double(3.14); creates double, not single. x = int32(3.14); creates integer, which truncates decimals. x = single '3.14'; is invalid syntax.

3. Final Answer:

   x = single(3.14); -> Option A

4. Quick Check:

   Use single() function for single precision [OK]

Hint: Use single() function to convert numbers to single [OK]

Common Mistakes:

• Using double() instead of single()
• Trying to assign string to single
• Using int32 for decimals

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

x = int8(127); y = x + 1; disp(y);

medium

A. -128

B. 128

C. Error: Overflow

D. 127

Solution

1. Step 1: Understand int8 range

   int8 stores integers from -128 to 127. Adding 1 to 127 causes overflow.

2. Step 2: Check overflow behavior

   In MATLAB, int8 overflow wraps around to the minimum value, so 127 + 1 becomes -128.

3. Final Answer:

   -128 -> Option A

4. Quick Check:

   int8 overflow wraps to -128 [OK]

Hint: int8 max is 127; adding 1 wraps to -128 [OK]

Common Mistakes:

• Expecting 128 (out of range)
• Expecting error on overflow
• Thinking value stays at 127

4. Consider this MATLAB code:

a = single(1.5); b = int16(a); disp(b);

What is the output and why?

medium

A. 1.5

B. 1

C. 2

D. Error: Cannot convert single to int16

Solution

1. Step 1: Convert single to int16 behavior

   When converting from single to int16, MATLAB truncates the decimal part (does not round).

2. Step 2: Apply truncation to 1.5

   Truncating 1.5 results in 1, so b becomes 1.

3. Final Answer:

   1 -> Option B

4. Quick Check:

   Conversion truncates decimals, so 1.5 -> 1 [OK]

Hint: Conversion truncates decimals, no rounding [OK]

Common Mistakes:

• Expecting rounding to 2
• Expecting error on conversion
• Expecting output as 1.5

5. You want to store a large array of numbers between 0 and 255 efficiently in MATLAB. Which numeric type should you choose to minimize memory while preserving all values exactly?

hard

A. double

B. single

C. uint8

D. int16

Solution

1. Step 1: Identify value range and memory needs

   Values are between 0 and 255, so an unsigned 8-bit integer (uint8) fits exactly.

2. Step 2: Compare types for memory and precision

   double and single use more memory and are floating-point. int16 uses 16 bits and allows negative values, wasting space.

3. Step 3: Choose the best type

   uint8 uses 8 bits, stores 0-255 exactly, and saves memory.

4. Final Answer:

   uint8 -> Option C

5. Quick Check:

   Use uint8 for 0-255 integer range to save memory [OK]

Hint: Use uint8 for 0-255 integers to save memory [OK]

Common Mistakes:

• Choosing double wastes memory
• Using int16 wastes space and allows negatives
• Using single loses integer precision