Extract numbers from mixed string

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K E
K E 2012-7-19
编辑： Angkur Shaikeea 2021-10-21
I have a file containing header lines like the following,
Test setup: MaxDistance = 60 m, Rate = 1.000, Permitted Error = 50
Operator Note: Air Temperature=20 C, Wind Speed 16.375m/s, Altitude 5km (Cloudy)
For a given parameter such as MaxDistance or Wind Speed, I would like to extract its numerical value. This is tricky because sometimes there is an equal sign, space, or units, and sometimes there is not, because different operators enter their notes differently (lesson: next time enforce consistency).
How would I extract the following: All numerical characters (ignoring spaces and equal signs but keeping decimal points) that appear after the string representing the parameter name. Stop when a letter or punctuation mark is reached. In the case of 'MaxDistance', I would obtain 60. In the case of Wind Speed, I would obtain 16.375.
  2 个评论
Albert Yam
Albert Yam 2012-7-19
编辑：John Kelly 2015-2-26
What have you tried?
Jianming She
Jianming She 2020-6-17
编辑：Jianming She 2020-6-18
This seems a more general way:
function numArray = extractNumFromStr(str)
str1 = regexprep(str,'[,;=]', ' ');
str2 = regexprep(regexprep(str1,'[^- 0-9.eE(,)/]',''), ' \D* ',' ');
str3 = regexprep(str2, {'\.\s','\E\s','\e\s','\s\E','\s\e'},' ');
numArray = str2num(str3);
Example:
a = 'alpha=-3.5,beta=1e-2. but gamma = -34.1'
numArray = extractNumFromStr(a)
numArray =
-3.5000 0.0100 -34.1000

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采纳的回答

Jan
Jan 2012-7-19
编辑：Jan 2012-7-19
Import the file into a string at first, e.g. by fileread. Then you get something like this (if not, please explain all necessary details):
Str = ['Test setup: MaxDistance = 60 m, Rate = 1.000, ', ...
'Permitted Error = 50 Operator Note: Air Temperature=20 C, ', ...
'Wind Speed 16.375m/s, Altitude 5km (Cloudy)'];
Now omit all equal characters:
Str(strfind(Str, '=')) = [];
Finally you can get the values:
Key = 'MaxDistance';
Index = strfind(Str, Key);
Value = sscanf(Str(Index(1) + length(Key):end), '%g', 1);
"Index(1)" cares for multiple occurences of the key.
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Jan
Jan 2012-7-19
The removing of the = is clear, I think. Then STRFIND looks for the wanted string. Afterwards the first number behind this string is extracted by SSCANF. Here "behind" means the position, where the string is found plus the number of characters the string have.
Lorenzo
Lorenzo 2013-10-30
This works great! Just a quick question Jan: what if you want to find all the uccurrence of a numeric value between two strings? For instance, let's say you want the numeric values that can be found between MaxDistance and Altitude in the original example (i.e. 60, 1000, 50 ecc ecc...). How can you achieve that?
I tried this:
Key1 = 'MaxDistance'; Key2 = 'Altitude'; Index1 = strfind(file, Key1); Index2 = strfind(file, Key2); Value = sscanf(file(Index1:Index2), '%g',1);
but still I can get nothing but the first value.... Also, I dont know a-priori the number of numbers that can be encontured between the two strings...
Thanks!
Lorenzo

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更多回答（5 个）

Stephan Koehler
Stephan Koehler 2017-6-7
Here is a one-line answer str2num( regexprep( Str, {'\D*([\d\.]+\d)[^\d]*', '[^\d\.]*'}, {'$1 ', ' '} ) )
Freddy
Freddy 2012-7-19
Maybe a little bit too late, but i like to present you also my ("regexp training"-) solution. :)
A = regexp(Str,'(?<Keyword>(?:\w+\s*\w+))\s*=?\s*(?<Value>\d+\.?\d*)','names');
s = struct();
for i = A,
s.(genvarname(i.('Keyword'))) = str2double(i.('Value'));
end
  1 个评论
Albert Yam
Albert Yam 2012-7-19
编辑：Albert Yam 2012-7-19
That took a long time for me to understand what you are doing. That's cool though.
How does it skip over 'Operator Note:' ?
Edit: Never mind I get it. It doesn't have anything for ':'. The '(?:\w' has nothing to do with a ':' in the string, it is grouping the token for 'up to two words'.

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Albert Yam
Albert Yam 2012-7-19
This is how I went about it, all steps included even the errors.
teststr = 'Test setup: MaxDistance = 60 m, Rate = 1.000, Permitted Error = 50 Operator Note: Air Temperature=20 C, Wind Speed 16.375m/s, Altitude 5km (Cloudy)';
regexp(teststr,[\d])
regexp(teststr,['\d'])
regexp(teststr,['\d'],'match')
regexp(teststr,['\d+'],'match')
regexp(teststr,['\d+.?'],'match')
regexp(teststr,['\d+\.?'],'match')
regexp(teststr,['\d+\.?\d?'],'match')
regexp(teststr,['\d+\.?\d+?'],'match')
regexp(teststr,['\d+\.?\d*?'],'match')
regexp(teststr,['\d+\.?\d?'],'match')
regexp(teststr,['\d+\.?\d*'],'match')
  6 个评论
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G
G 2013-11-7
编辑：G 2013-11-13
Better:
regexp(teststr,'\d+\.?\d*|-\d+\.?\d*|\.?\d+|-\.?\d+','match')
or
regexp(teststr,'-?\d+\.?\d*|-?\d*\.?\d+','match')
remains the -.34e-004 case !
Angkur Shaikeea
Angkur Shaikeea 2021-10-21
编辑：Angkur Shaikeea 2021-10-21
i need to extract
0.00000 0.00000 0.00000
0.00000 1.00000 0.00000
1.00000 0.00000 0.00000
from a text file containing
.............................................
Nodal positions:
0.00000 0.00000 0.00000
0.00000 1.00000 0.00000
1.00000 0.00000 0.00000
Nodal positions:
0.00000 0.00000 0.00000
0.00000 1.00000 0.00000
1.00000 0.00000 0.00000
Nodal positions:
0.00000 0.00000 0.00000
0.00000 1.00000 0.00000
1.00000 0.00000 0.00000
any help using regexp?

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C.J. Harris
C.J. Harris 2012-7-19
In order to extract a certain value:
Str = ['Test setup: MaxDistance = 60 m, Rate = 1.000, ', ...
'Permitted Error = 50 Operator Note: Air Temperature=20 C, ', ...
'Wind Speed 16.375m/s, Altitude 5km (Cloudy)'];
matchWord = 'Air Temperature';
[a,b] = regexp(Str,'\d+(\.\d+)?');
strPos = find(a > strfind(Str,matchWord),1,'first');
nValue = str2double(Str(a(strPos):b(strPos)));
Dahai Xue
Dahai Xue 2016-3-10
编辑：KSSV 2021-1-25
C.J. Harris, I put your regexp into a function to extract all numbers using regexp. I have hard time to find an array operation that can use the 'a' and 'b' without the loop. Hopefully somebody has ideas. Of course it is not difficult to add more parameters or options to find "certain" numbers with preceding or following landmark strings.
function nums = regExtractNums(str)
[a,b] = regexp(str, '\d+(\.\d+)?');
nums = zeros(length(a),1);
for k = 1:length(a)
nums(k) = str2double(str(a(k):b(k)));
end
end

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