How to extract a number from a string array?

2018 6 21
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更新时间：2018 6 21
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I have a string array of values that look like this: "(164) - (165)" "(165) - (166)" "(165) - (166)" How can extract the first three digit value only so that I get a matrix that is 164 165 165

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Dayne Coleman
Dayne Coleman 2018-6-21
编辑：Dayne Coleman 2018-6-21
I am also trying to turn a string of Dates and times into a floating point value corresponding to the time. I have a string array that looks like: "Mon Jun 04 16:18:38 EDT 2018" "Mon Jun 04 16:33:29 EDT 2018" and I need a number array that has a decimal for the time of day. (12:00 am would be 0.000, noon would be 0.500)
Juan Fernandez
Juan Fernandez 2018-6-21
编辑：Juan Fernandez 2018-6-21
Have you looked through the documentation page for the sscanf(_) function? That might provide you a solution.
Dayne Coleman
Dayne Coleman 2018-6-21
Yes, I have tried sscanf(_). I don't know if it's a problem with my indexing or the function itself. Here is what I have:
>> whos str_node
Name Size Bytes Class Attributes
str_node 92x1 7248 string
node=sscanf(str_node(:,1),'%f')
I'm getting an error that reads:
"First argument must be a string scalar or character vector."
Dayne Coleman
Dayne Coleman 2018-6-21
I got it to work using the strtok(_) function below. Let me know if there are faster, more efficient ways of doing it.
[token,remain]=strtok(str_node,'0,1,2,3,4,5,6,7,8,9');
parsed_node=strtok(remain,')');
node=str2double(parsed_node(:));

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Stephen23
Stephen23 2018-6-21
编辑：Stephen23 2018-6-21

1 个投票

"How can extract the first three digit value only so that I get a matrix that is 164 165 165"
With a simple application of regexp and str2double:
>> C = {'(164) - (165)','(165) - (166)','(165) - (166)'};
>> str2double(regexp(C,'\d{3}','match','once'))
ans =
164 165 165

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Juan Fernandez
Juan Fernandez 2018-6-21

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I searched through older questions and found a similar one from 2012. The solution requires the use of regexp(_). Here's my implementation.
str1 = '(164) - (165)';
str2 = '(165) - (166)';
str3 = '(165) - (166)';
strs = {str1,str2,str3};
output = zeros(length(strs),1);
for iter=1:length(strs)
num_strs = regexp(strs{iter},'\d*','Match');
output(iter) = str2double(num_strs{1});
end

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