[R] XML package- accessing nodes based on attributes

[Skewes,Aaron]

Hi,

I have a rather complex xml document that I am attempting to parse based on 
attributes:

<Manifest xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";>
  <!-- eName       : name of the element.
      eValue       : value of the element. -->
  <OutputFilePath>D:\CN_data\Agilent\Results\</OutputFilePath>
  <FilesList>
    <File>
        <Characteristic Type="File" eName="FileTypeId" eValue="10"/>
                <Characteristic Type="File" eName="FilePath" 
eValue="D:\CN_data\Agilent\TCGA-06-0875-01A-01D-0387-02_US23502331_251469343372_S01_CGH-v4_10_Apr08.txt"/>
                <Characteristic Type ="Patient" eName="PatientReference" 
eValue="TCGA-06-0875-01A"/>
                <Characteristic Type ="Patient" eName="SampleType" 
eValue="TUMOR"/>
                <Characteristic Type ="Patient" eName="SampleMarker" 
eValue="cy3"/>
                <Characteristic Type ="Patient" eName="PatientDateOfBirth" 
eValue="080808"/>
                <Characteristic Type ="Patient" eName="PatientGender" 
eValue="M"/>
                <Characteristic Type ="Patient" 
eName="PatientSampleConcentration" eValue="20mg"/>
    </File>
File>
        <Characteristic Type="File" eName="FileTypeId" eValue="10"/>
                <Characteristic Type="File" eName="FilePath" 
eValue="D:\CN_data\Agilent\TCGA-06-0875-01A-01D-0387-02_US23502331_251469343372_S02_CGH-v4_10_Apr08.txt"/>
                <Characteristic Type ="Patient" eName="PatientReference" 
eValue="TCGA-06-0875-02A"/>
                <Characteristic Type ="Patient" eName="SampleType" 
eValue="TUMOR"/>
                <Characteristic Type ="Patient" eName="SampleMarker" 
eValue="cy3"/>
                <Characteristic Type ="Patient" eName="PatientDateOfBirth" 
eValue="080808"/>
                <Characteristic Type ="Patient" eName="PatientGender" 
eValue="M"/>
                <Characteristic Type ="Patient" 
eName="PatientSampleConcentration" eValue="20mg"/>
    </File>

    <File>
                <Characteristic Type="File" eName="FileTypeId" eValue="20"/>
                <Characteristic Type="File" eName="FilePath" 
eValue="D:\CN_data\Agilent\TCGA-06-0875-10A-01D-0387-02_US23502331_251469342195_S01_CGH-v4_10_Apr08.txt"/>
                <Characteristic Type ="Patient" eName="PatientReference" 
eValue="TCGA-06-0875-10A"/>
                <Characteristic Type ="Patient" eName="SampleType" 
eValue="NORMAL"/>
                <Characteristic Type ="Patient" eName="SampleMarker" 
eValue="cy3"/>
                <Characteristic Type ="Patient" eName="PatientDateOfBirth" 
eValue="080808"/>
                <Characteristic Type ="Patient" eName="PatientGender" 
eValue="M"/>
                <Characteristic Type ="Patient" 
eName="PatientSampleConcentration" eValue="20mg"/>
    </File>


My requirement is to access eValues at each <File> node based on FileTypeId. 
For example:

How can I get the eValue of eName="PatientReference" for all Type="Patient" 
,where the <Characteristic Type="File" eName="FileTypeId" eValue="10"/>?

i.e. "TCGA-06-0875-01A" and "TCGA-06-0875-02A"


For the life of me, I can not get this to work!

Thanks,
-Aaron



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