extracting numbers from a string in an array
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Hi,
I have an array, p, approximately 1200 rows long, and inside each cell in the array is a string with a number inside it, for example:
p(3,1)=
'"rainfall":0.1'
For each cell in the array I am trying to extract the number value. So for the above case I want the cell to simply have the number 0.1
Any ideas on how to do this? The length of the strings in each cell will be the same length, and have exactly the same characters - the only thing that changes is the number.
Many Thanks,
Sam
采纳的回答
Andrei Bobrov
2012-9-20
out = cellfun(@(x)str2double(regexp(x,'\d*\.\d*','match')),p);
更多回答（1 个）
I assume this is faster than the regexp approach:
p = {'"rainfall":0.1', '"rainfall":0.2', '"rainfall":0.333'};
s = sprintf('%s*', p{:});
numbers = sscanf(s, '"rainfall":%g*');
Alternative, which could be faster also:
q = strrep(p, '"rainfall":', '');
s = sprintf('%s*', p{:});
numbers = sscanf(s, '%g*');
To avoid a hardcoding of the string '"rainfall":':
index = strfind(p{1}, ':');
key = p{1}(1:index(end));
q = strrep(p, key, '');
5 个评论
Sam harris
2012-9-20
Jan
2012-9-20
No problem, Sam. Andrei's solution is fine and REGEXP is more powerful. I've posted the SSCANF(SPRINTF) approach, because it is simple and surprisingly fast.
shapes
2012-10-13
Hi ppl,
My problem is in a way similar and not...i am reading a text file consisting of various lines of alpha-numeric strings... N010 G00 X0 Y0 Z0 N020 G01 X-10 Y10 Z-1 N030 G01 X20 Y40 Z-1 N040 G04 X3 Y3 Z10 M03
Now I need all numerical values of X, i.e. -10,20,3. The problem I am facing is that the strings are read from text file as 'cell' vector and i have to convert them to 'char' to use 'regexp' using '\w*X\w*'....this works, but doesnot allow the negative number to be read because it starts with a '-'. What to do now??? can anybody help??
shapes
2012-10-13
for simplicity lets consider N040 G04 X-3 Y3 Z10 M03
K E
2012-11-8
Start a new question, and you are more likely to get an answer.
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