MATLAB - Text Formatting

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Text formatting comes into picture when you want to display the text in a specific format.

Matlab makes use of formatting operators to manage with the notation, alignment , significant digits etc. The functions num2str and sprintf are mostly used methods that take care of text formatting using formatting operators.

For example formatting operator like −

%f is used to convert floating point values to text using fixed-point notation.

%.2f is used to represent 2 digits after the decimal point.

%12f is used to show 12 characters in the output , padding and spaces.

In Matlab the functions with formatting operators support are compose, num2str, sprintf, fprintf.

Formatting Operator Fields

There are in total six fields for a formatting operator. Here is the details of it

The formatting operator six fields consists of Identifier, Flags, Field width ,Precision, Subtype and Conversion Character.From the six fields conversion character is the only mandatory param that goes along with the leading % character.

Conversion Character

The conversion character tells about the output notation. It takes a single character and is at the last in the format specifier.

Here is an example using conversion characters wherein will format the number to display in Hexadecimal form.

>> N = 30*ones(1,3);
text_format = sprintf('%X', N)

text_format =

    '1E1E1E'

>> 

To get the decimal and fixed point formatting of the same number you can make use of %d and %f in the sprintf method as shown below.

>> N = 30*ones(1,3);
>> text_format = sprintf('%d %f', N)

text_format =

    '30 30.00000030 '

>> 

Subtype

Subtype is a single alphabet that just comes before the conversion character.Without subtype the conversion specifiers like %o, %x, %X, and %u will consider the input data given as integers.

So to consider the input data to be floating point instead of integers and to convert them to octal, decimal, or hexadecimal you can consider below subtype specifiers

Example

>> N = 15;
>> text_format = sprintf('%bu', N)

text_format =

    '04624633867356078080'

Precision

This field immediately follows a period in the formatting operator. The number used is 0 or a positive integer. For example %6.3f here the precision is 3.

Example

>> text_format = sprintf('%.2f', 1500)

text_format =

    '1500.00'

>> 

Field Width

Is the positive integer in the formatting operating field width that tells about the number of digits or characters in the output. For example %5.2f , here the field width is 5.

By default you will space padded at the left side , If the field width is greater than the number of characters to be displayed.

Example 1

>> text_format = sprintf('|%3e|%f|%5f|',[33333 45454 50.12123])

text_format =

    '|3.333300e+04|45454.000000|50.121230|'
>> 

Example 2

>> text_format = sprintf('%20s', 'Hello world')

text_format =

    'Hello world'

>> 

Flags

This field is optional but using it can give you additional formatting to your output. The table below describes the characters you can make use of during the formatting.

Example 1: Using the minus sign (-)

>> txt_format = sprintf('Example of left-justify: %-12.2f',11.3)

txt_format =

    'Example of left-justify: 11.30       '

>>

Example 2: Using the plus sign (+)

>> text_format = sprintf('plus sign: %+5.2f',12.3)

text_format =

    'plus sign: +12.30'

>> 

Example 3: Using Space for Padding

>> mytxt = sprintf('Padding with zeroes: %010.2f',5.2)

mytxt =

    'Padding with zeroes: 0000005.20'

>> 

Example 4: Using Zero(0) for Padding

>> mytxt = sprintf('Padding with zeroes: %010.2f',5.2)

mytxt =

    'Padding with zeroes: 0000005.20'

>> 

Identifier

An identifier refers to a name given to a variable, function, or other element in the code. When it comes to text formatting, an identifier can be used to specify the location where a value should be inserted within a formatted string.

To include an identifier in text formatting in MATLAB, you can use the % character followed by a number (or optional name) that specifies the position of the corresponding argument in the input argument list.

Example

>> a = 'My age is: ';
b = 25;

mystr = sprintf('%s %d', a, b)

mystr =

    'My age is:  25'

>> 

Text Formatting using compose() Method

The compose() function in MATLAB takes a format specifier string as its first argument, and one or more values or variables as subsequent arguments. It returns a formatted string by replacing the placeholders in the format specifier with the provided values.

Example

a = 'My age is: ';
b = 25;

mystr = compose('%s %d', a, b)

On execution in matlab the output is

>> a = 'My age is: ';
b = 25;

mystr = compose('%s %d', a, b)

mystr =

  11 cell array

    {'My age is:  25'}

>> 

Text Formatting using num2str() Method

The num2str() function in MATLAB is used for converting numeric values to their corresponding string representations. It takes one or more numeric input values and returns a string representation of those values.

The basic syntax for num2str is −

str = num2str(value, format)

• value represents the numeric value or array that you want to convert to a string.
• format (optional) specifies the format of the resulting string. It can be a format specifier like '%d' for integers or '%0.2f' for floating-point numbers, among others.

Example

pi_value = 3.14159;
str = num2str(pi_value, '%0.3f')

On execution in matlab you will get

>> pi_value = 3.14159;
str = num2str(pi_value, '%0.3f')

str = 3.142

>> 

Text Formatting using fprintf() Method

The fprintf() function in MATLAB is used for writing formatted data to a file or the command window. It allows you to combine text and data in a flexible and organized manner.

The basic syntax of fprintf() is −

fprintf(format, A1AN)

• format is a string that specifies the format of the output. It consists of static text and format specifiers, such as %s, %d, %f, or %e, that represent the placeholders for the corresponding data in A.
• A1..AN is the data to be written, which can be a scalar, vector, matrix, or cell array.

Example

a = 'My age is: ';
b = 25;

fprintf('%s %d', a, b)

On execution in matlab you will get

>> a = 'My age is: ';
b = 25;

fprintf('%s %d', a, b)

My age is:  25
>>