How to structure the data using webread

Hi, I will have to automatize a procedure to extract data from different URLs, One example of the URL link is the following:

url='https://earthquake.usgs.gov/fdsnws/event/1/query?format=quakeml&eventid=us6000n8tq',

data=webread(url);

The variable data has a huge amount of information that I would like to structure in order to access and retrieve the data easily without the need of creating a xml file.

I would appreciate the help.

Answer 1

[Ayush Aniket]

Hi Jorge,

To retrieve specific data from the XML file, you can use regexp on the string output of webread function. Refer the following MATLAB answer for an example: https://www.mathworks.com/matlabcentral/answers/883153-how-to-extract-the-data-from-webread-output

You may also refer the following link to understand more about the regexp function: https://www.mathworks.com/matlabcentral/answers/402062-help-using-regexp?#answer_321487

[Jorge Luis]

Thank you very much. Yes, that was the other option I was tempted to use but considering all the amount of data, I wanted a way in which all the information is converted in a structure matrix. I managed to do that but you need to save the data and use functions to write a xlm file and then structure the file.

Answer 2

[Anshuman]

First you can parse the data to xmlData:

% Convert the data from char to XML DOM
xmlData = xmlreadstring(data);

You can use XPath queries to extract specific elements from the XML data:

% Create an XPath factory and compile the XPath expression
factory = javax.xml.xpath.XPathFactory.newInstance;
xpath = factory.newXPath;

% Extract magnitude
magnitudeExpression = xpath.compile('//magnitude/mag/value');
magnitudeNode = magnitudeExpression.evaluate(xmlData, javax.xml.xpath.XPathConstants.NODE);
magnitude = str2double(magnitudeNode.getTextContent);

This way you can extract the specific data like magnitude and any other information as needed.

[Jorge Luis]

Much appreciated. I am still looking for the way of saving the files as xlm witouth saving the webread data in order to structure all the information using the following function: https://www.mathworks.com/matlabcentral/fileexchange/28639-struct2xml.

[Jorge Luis]

The function xmlreadstring does not work.