MATLAB: Parsing file names and converting to numbers

parsingstring manipulationstring to numeric

Hello,

I have a series of bitmap image files each with a velocity as the first 5 characters in the filename (see attached). I seem to be able to isolate the 15.36 from the first file but when I put into a loop in the editor it doesn't like that. Is there a way to parse a filename based on position and write the strings to a numeric variable?

thanks

Best Answer

str2double(filename(1:5))

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MATLAB: Parser.

It depends. If the contents in the text file have a consistent format, many times using d=importdata('DataFile.txt') is sufficient to put the numerical data and text data aside. You can even use d=uiimport to go through it once manually and have the option to generate the code for it so you can apply it to other similar files.

If the format is not consistent, using textscan(fid,'%f') can skip the text strings.

MATLAB: How to remove leading and trailing spaces from a string

To remove leading and trailing spaces from the string, you can use the DEBLANK function:

str = '   Hello, World!   '
str = deblank(str)  %remove trailing spaces
str_flipped = str(end:-1:1)  %flip the string
str_flipped = deblank(str_flipped)  %remove trailing spaces of the flipped string
str = str_flipped(end:-1:1)  %flip the string back

The resulting string does not contain any leading or trailing spaces:

str
 str = 'Hello, World!'

To remove leading spaces from the string, you can also use the STRTOK function, which finds the first token in the string. (A token is the first set of characters that is encountered before a delimiter. In the following example, it is white space.) Leading delimiters are ignored. For example:

str = '   Hello   '
str_new = strtok(str)

The first token of the string 'str' without any leading spaces is found:

str_new
 str_new = 'Hello'

If you have a string containing more than one token and want to remove leading spaces from the string, you can use STRTOK in the following format:

 [token,rem] = strtok(str)

where 'str' is the input string, 'token' is the first token, and 'rem' is the remainder. Then combine the outputs 'token' and 'rem'.

For example:

str = '   Hello, World!'
[t,r] = strtok(str)
str_new = [t r]

Here is the output:

 t = 'Hello,'
 r = ' World!'
 str_new = 'Hello, World!'

For more information on these functions, type 'help function_name' at the MATLAB command prompt. If you have installed the documentation, type 'doc function_name' to see the documentation for these functions. If you do not have the documentation installed, you can find it here:

http://www.mathworks.com/access/helpdesk/help/techdoc/matlab.shtml

Simply type the function name in the search box.

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MATLAB: Parser.

MATLAB: How to remove leading and trailing spaces from a string

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