MCA data in SPEC file

[dschick]

Hi @dkriegner ,

I encountered a problem in SPEC files which contain MCA data. For know I am trying to understand the way the MCA data is read. I noticed that there is no special case for the @A marker which should indicate a line of MCA data.

I think the current implementation does not assume a mixture of MCA and usual scalar data, right?

I will draft a PR if I am a bit more into the code.

Best

Daniel

[dkriegner]

For sure MCA data worked at some point. but i did not encounter such files for a long time. of course a PR is always welcome but it would be better to first explore why it does not work for you.

On Thu, 5 Aug 2021, 09:50 Daniel Schick, @.***> wrote:

Hi @dkriegner https://github.com/dkriegner ,

I encountered a problem in SPEC files which contain MCA data. For know I am trying to understand the way the MCA data is read. I noticed that there is no special case for the @A marker which should indicate a line of MCA data.

I think the current implementation does not assume a mixture of MCA and usual scalar data, right?

I will draft a PR if I am a bit more into the code.

Best

Daniel

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[dschick]

thanks for your promt reply.

As I said, the @A marker is not respected while parsing the file. Also the parsers does not seem to like a mixture of MCA and scalar data it distinguishes like

if self.has_mca

else

This is true for setting the column names and the actual data which are eventually converted to the numpy array

[dkriegner]

Hi Daniel,

you are right that the parser does not explicitly detect the @A marker. somehow this was not necessary so far because the information from the @MCA line and the channel number was sufficient. And of course a mixture of scalar and MCA data also worked for me. for example in the hello world example: https://xrayutilities.sourceforge.io/index.html#hello-world (the respective data file can be found in the examples/data/test.spec.bz2 file)

If the current implementation fails with newer files a PR is of course welcome. I would be glad if these existing data files could still be parsed. I think the respective unit test in tests/test_io_spec.py needs to be improved to also test the MCA data in a test file. In fact the current file used already contains MCA data, but the tests seems to ignore them at the moment.

[dschick]

Hi Dominik,

I found some time to dive into the MCA problem. Indeed the current version of xrayutilities allows for reading the MCA from test SPEC file.

The issue actually arises again from how Sardana is implemnting the MCAs vs. SPEC. So Sardana allows for multiple MCAs in one scan as SPEC seems to allow only for one. In order to allow for multiple MCAs Sardana provides an additional identifier @DET_X where X is an integer and after the identifier the name of the MCA is provided.

Since the @CHANN identifier is also given just once, it means, that all MCAs in the Sardana implementation should have the same lengh (which is actually not checked for). However, for reading the Sardana MCAs the @CHANN is not really necessary, as there is no line-breaking available as in SPEC and each MCA data line in the scan starts with an @A which allows to read the MCA data line by line.

Moreover the order of scalar and MCA data is swapped/flexible in Sardana.

I made a PR which allows for both types of MCAs and here is also a Sardana test file

[lrlunin]

Hello, just encounted this issue in the version 1.7.6

Exception occurs in ReadData() method.

[dkriegner]

Does the code in #129 fix the issue for you?

[lrlunin]

Yes, I could successfully read the data from .spec file.

[dkriegner]

Ok, I look into merging the mentioned PR and include it in a release.