R import XML from Graphpad Prism

I am trying to import raw data from Graphpad Prism .pzfx files, which in principle are .xml files. I took out most of the prism specific stuff and left just the part I am interested in.:

<?xml version="1.0" encoding="UTF-8"?>
<GraphPadPrismFile xmlns="http://ift.tt/1AQDJWT" PrismXMLVersion="5.00">
  <TableSequence Selected="1">
    <Ref ID="Table0" Selected="1"/>
  </TableSequence>
  <Table ID="Table0" XFormat="error" YFormat="replicates" Replicates="1" TableType="XY" EVFormat="AsteriskAfterNumber">
    <Title>Data 1</Title>
    <XColumn Width="162" Decimals="0" Subcolumns="1">
      <Title>X</Title>
      <Subcolumn>
        <d>1</d>
        <d>2</d>
        <d>3</d>
        <d>4</d>
      </Subcolumn>
    </XColumn>
    <YColumn Width="81" Decimals="4" Subcolumns="1">
      <Title>ML</Title>
      <Subcolumn>
        <d>120</d>
        <d>100</d>
        <d>5</d>
        <d>0</d>
        <d>1.5</d>
      </Subcolumn>
    </YColumn>
    <YColumn Width="81" Decimals="4" Subcolumns="1">
      <Title>MH</Title>
      <Subcolumn>
        <d>10</d>
        <d>560</d>
        <d>665</d>
        <d>40</d>
        <d>31.5</d>
      </Subcolumn>
    </YColumn>
    <YColumn Width="81" Decimals="6" Subcolumns="1">
      <Title>MH2</Title>
      <Subcolumn>
        <d>1.20</d>
        <d>100</d>
        <d>5</d>
        <d>0</d>
        <d>1.5</d>
      </Subcolumn>
    </YColumn>
    <YColumn Width="81" Decimals="6" Subcolumns="1">
      <Title>MH1</Title>
      <Subcolumn>
        <d>120</d>
        <d>100</d>
        <d>5</d>
        <d>0</d>
        <d>1.5</d>
      </Subcolumn>
    </YColumn>
  </Table>
</GraphPadPrismFile>

To my understanding I have a Node Table which again has XColumn, YColumn nodes, which have Title and then have Subcolumn nodes. Those contain my raw data I would like to convert into a R-data.frame.

So far I have managed to import one YColumn: (file is the path to the one above)

xData <- xmlParse(file)
xData.rt <- xmlRoot(xData)
xmlToDataFrame(xData.rt[["Table"]][["YColumn"]][["Subcolumn"]])

This gives me the first YColumn as a data.frame:

  text
1  120
2  100
3    5
4    0
5  1.5

Is there a (maybe also simpler?) way to import all X and Y Colums into one data.frame?