extracting data from within xml files using MATLAB

Question

I am a complete programming beginner trying to learn MATLAB. I want to extract numerical data from a bunch of different xml files. The numerical data items are bounded by the tags and . How do I write a program in MATLAB?

My algorithm:

1. Open the folder
2. Look into each of 50 xml files, one at a time
3. Where the tag <HNB.1></HNB.1> exists, copy numerical contents between said tag and write results into a new file
4. The new file name given for step 3 should be the same as the initial file name read in Step 2, being appended with "_data extracted"

example:

FileName = Stewart.xml
Contents = blah blah blah <HNB.1>2</HNB.1> blah blah
NewFileName = Stewart_data extracted.txt
Contents = 2

Answer 1

The fundamental function in MATLAB to read xml data is xmlread; but if you're a complete beginner, it can be tricky to work with just that. Try this series of blog postings that show you how to put it all together.

Answer 2

Suppose you want to read this file:

<PositiveSamples numImages="14">
<image numSubRegions="2" filename="TestingScene.jpg">
	<subregion yStart="213" yEnd="683" xStart="1" xEnd="236"/>
	<subregion yStart="196" yEnd="518" xStart="65" xEnd="226"/>
</image>
</PositiveSamples>

Then in matlab, read the file contents as follows:

%read xml file
xmlDoc = xmlread('PositiveSamples.xml');

%Get root element
root = xmlDoc.getDocumentElement();

%Read attributevale
numOfImages = root.getAttribute('numImages');
numOfImages = char(numOfImages);   
numOfImages = uint16(eval(numOfImages));