extract 2 data(temperature) from string

Question

Jeong_evolution 2016-10-29

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/309729-extract-2-data-temperature-from-string

编辑： per isakson 2016-10-29

Code is

Str = [' <data seq="0"  <temp8.0</temp  <data seq="1"   <temp6.9</temp '];
Str(strfind(Str, '>')) = [];
Key_1   = '<temp';
Index_1 = strfind(Str, Key_1);
Value_1 = sscanf(Str(Index_1 + length(Key_1):end),'%f');

But this code express in workspace

Value_1 = 8

I want to express in workspace

Value_1 = 8
Value_2 = 6.9

How can I make code ?

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Answer 1

per isakson 2016-10-29

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https://ww2.mathworks.cn/matlabcentral/answers/309729-extract-2-data-temperature-from-string#answer_241258

编辑：per isakson 2016-10-29

在 MATLAB Online 中打开

Use regexp to match strings which

follow after the string "<temp"
consist of (digit,period,digit)
are followed by "</temp"

str = [' <data seq="0"  <temp8.0</temp  <data seq="1"   <temp6.9</temp '];
cac = regexp( str, '(?<=<temp)\d\.\d(?=</temp)', 'match' );
temp_2 = str2double(cac{2})
temp_1 = str2double(cac{1})

outputs

temp_2 =
    6.9000
temp_1 =
     8
>>

Or use sscanf. The format_string is a copy of Str, in which the "numbers" you want to extract are replaced by the specifier, %f

num = sscanf( Str, '<data seq="0"  <temp%f</temp  <data seq="1"   <temp%f</temp' )

which outputs

num =
    8.0000
    6.9000
>>

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dpb 2016-10-29

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Good...somebody that does know regular expressions... :) I'd note for OP that can wrap the above in str2double and avoid the named variable issues cleanly...

>> str2double(regexp( Str, '(?<=<temp)\d\.\d(?=</temp)', 'match' ))
ans =
  8.0000    6.9000
>>

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Answer 2

dpb 2016-10-29

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https://ww2.mathworks.cn/matlabcentral/answers/309729-extract-2-data-temperature-from-string#answer_241239

编辑：dpb 2016-10-29

在 MATLAB Online 中打开

This would be a good place for regular expressions, but I'm a dweeb when it comes to trying to write the proper parsing expression...with string operations, I'd do this something like--

>> Str = [' <data seq="0"  <temp8.0</temp  <data seq="1"   <temp6.9</temp '];
>> t=tokens(Str,'<');
>> Values=str2num(t(t(:,1)=='t',5:end))
Values =
  8.0000
  6.9000
>>

The above takes advantage that the string 'temp' trailing the value is returned with the leading '/' so the first character in the resulting array of tokens being 't' identifies the desired rows. Then, since it's a fixed-length string of four leading characters, simply return the remainder of the string '5:end' and convert to numeric.

tokens is my little utility routine--

>> type tokens
function tok = tokens(s,d)
%   Simple string parser returns tokens in input string s
%
%   T=TOKENS(S) returns the tokens in the string S delimited
%   by "white space".  Any leading white space characters are ignored.
%
%   TOKENS(S,D) returns tokens delimited by one of the
%   characters in D.  Any leading delimiter characters are ignored.
% Get initial token and set up for rest
if nargin==1
  [tok,r] = strtok(s);
  while ~isempty(r)
    [t,r] = strtok(r);
    tok = strvcat(tok,t);
  end
else
  [tok,r] = strtok(s,d);
  while ~isempty(r)
    [t,r] = strtok(r,d);
    tok = strvcat(tok,t);
  end
end
>>

NB: It's a very bad idea to "poof" variables into the workspace with names such as you've written; it leads to requiring eval to process them later and that just leads to a location where "there be dragons" and is to be avoided. Use an array as shown instead.