[轉]matlab fprintf 中%tx %f %e

最近在搞一個項目用到浮點運算，做仿真對比時，看到fprintf(fid,'%tx'),一下就懵圈了，查了很多資料都沒講，幸遇以下文章，講的很詳細。

【轉自】http://blog.sina.com.cn/s/blog_50363a790100x2tn.html

MATLAB中將數據寫入文本文件的函數fprintf

  (2012-03-27 08:17:57)

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標簽：  雜談

分類： MATLAB

 

函數格式：fprintf(fileID, format, A, ...)；fprintf(format, A, ...)；count = fprintf(...)

fprintf(fileID, format, A, ...) applies the format to all elements of array A and any additional array arguments in column order, and writes the data to a text file. fprintf uses the encoding scheme specified in the call to fopen.

fprintf(format, A, ...) 格式化數據並將其結果顯示在屏幕上。

count = fprintf(...) 返回fprintf寫的字節個數。

Input Arguments

fileID

One of the following:

• An integer file identifier obtained from fopen.

• 1 for standard output (the screen).

• 2 for standard error.

Default: 1 (the screen)

format

String in single quotation marks that describes the format of the output fields. Can include combinations of the following:

• Percent sign followed by a conversion character, such as '%s' for strings.

• Operators that describe field width, precision, and other options.

• Literal text to print.

• Escape characters, including:

  ''	Single quotation mark
  %%	Percent character
  \\	Backslash
  \a	Alarm
  \b	Backspace
  \f	Form feed
  \n	New line
  \r	Carriage return
  \t	Horizontal tab
  \v	Vertical tab
  \xN	Hexadecimal number,N
  \N	Octal number, N

Conversion characters and optional operators appear in the following order (includes spaces for clarity):

The following table lists the available conversion characters and subtypes.

Value Type	Conversion	Details
Integer, signed	%d or %i	Base 10 values
	%ld or %li	64-bit base 10 values
	%hd or %hi	16-bit base 10 values
Integer, unsigned	%u	Base 10
	%o	Base 8 (octal)
	%x	Base 16 (hexadecimal), lowercase letters a–f
	%X	Same as %x, uppercase letters A–F
	%lu %lo %lx or %lX	64-bit values, base 10, 8, or 16
	%hu %ho %hx or %hX	16-bit values, base 10, 8, or 16
Floating-point number	%f	Fixed-point notation
	%e	Exponential notation, such as3.141593e+00
	%E	Same as %e, but uppercase, such as3.141593E+00
	%g	The more compact of %e or %f, with no trailing zeros
	%G	The more compact of %E or %f, with no trailing zeros
	%bx or %bX %bo %bu	Double-precision hexadecimal, octal, or decimal value Example: %bx prints pi as 400921fb54442d18
	%tx or %tX %to %tu	Single-precision hexadecimal, octal, or decimal value Example: %tx prints pi as 40490fdb
Characters	%c	Single character
	%s	String of characters

Additional operators include:

• Field width

  Minimum number of characters to print. Can be a number, or an asterisk (*) to refer to an argument in the input list. For example, the input list ('d', intmax) is equivalent to ('%*d', 12, intmax).

• Precision

  For %f, %e, or %E:	Number of digits to the right of the decimal point. Example: '%6.4f' prints pi as '3.1416'
  For %g or %G	Number of significant digits. Example: '%6.4g' prints pi as ' 3.142'

  Can be a number, or an asterisk (*) to refer to an argument in the input list. For example, the input list ('%6.4f', pi) is equivalent to ('%*.*f', 6, 4, pi).

• Flags

  Action	Flag	Example
  Left-justify.	'–'	%-5.2f
  Print sign character (+ or –).	'+'	%+5.2f
  Insert a space before the value.	' '	% 5.2f
  Pad with zeros.	'0'	.2f
  Modify selected numeric conversions: For %o, %x, or %X, print 0, 0x, or 0X prefix. For %f, %e, or %E, print decimal point even when precision is 0. For %g or %G, do not remove trailing zeros or decimal point.	'#'	%#5.0f

• Identifier

  Order for processing inputs. Use the syntax n$, where n represents the position of the value in the input list.

  For example, '%3$s %2$s %1$s %2$s' prints inputs 'A', 'B', 'C' as follows: C B A B.

The following limitations apply to conversions:

• Numeric conversions print only the real component of complex numbers.

• If you apply an integer or string conversion to a numeric value that contains a fraction, MATLAB overrides the specified conversion, and uses %e.

• If you apply a string conversion (%s) to integer values, MATLAB converts values that correspond to valid character codes to characters. For example, '%s'converts [65 66 67] to ABC.

• Different platforms display exponential notation (such as %e) with a different number of digits in the exponent.

  Platform	Example
  Windows	1.23e+004
  UNIX	1.23e+04

• Different platforms display negative zero (-0) differently.

  	Conversion Character
  Platform	%e or %E	%f	%g or %G
  Windows	0.000000e+000	0.000000	0
  Others	-0.000000e+00	-0.000000	-0

A

Numeric or character array.

Examples

Print multiple values and literal text to the screen:

B = [8.8 7.7 ; ... 8800 7700]; fprintf('X is %4.2f meters or %8.3f mm\n', 9.9, 9900, B)

MATLAB displays:

X is 9.90 meters or 9900.000 mm X is 8.80 meters or 8800.000 mm X is 7.70 meters or 7700.000 mm

Explicitly convert double-precision values with fractions to integer values, and print to the screen:

a = [1.02 3.04 5.06]; fprintf('%d\n', round(a));

Write a short table of the exponential function to a text file called exp.txt:

x = 0:.1:1; y = [x; exp(x)]; % open the file with write permission fid = fopen('exp.txt', 'w'); fprintf(fid, '%6.2f .8f\n', y); fclose(fid); % view the contents of the file type exp.txt

MATLAB import functions, all UNIX applications, and Microsoft Word and WordPad recognize '\n' as a newline indicator. However, if you plan to read the file with Microsoft Notepad, use '\r\n' to move to a new line when writing. For example, replace the previous call to fprintf with the following:

fprintf(fid, '%6.2f .8f\r\n', y);

On a Windows system, convert PC-style exponential notation (three digits in the exponent) to UNIX-style notation (two digits), and print data to a file:

a = [0.06 0.1 5 300] % use sprintf to convert the numeric data to text, using %e a_str = sprintf('%e\t',a) % use strrep to replace exponent prefix with shorter version a_str = strrep(a_str,'e+0','e+'); a_str = strrep(a_str,'e-0','e-'); % call fprintf to print the updated text strings fid = fopen('newfile.txt','w'); fprintf(fid, '%s', a_str); fclose(fid); % view the contents of the file type newfile.txt

Display a hyperlink (The MathWorks Web Site) on the screen:

site = 'http://www.mathworks.com'; title = 'The MathWorks Web Site'; fprintf('<a href = "%s">%s</a>\n', site, title)