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add field static_phi_list to NXxpcs #1314

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add field static_phi_list to NXxpcs #1314

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7297b4d
MNT #1313 add missing field
prjemian Oct 11, 2023
de32394
DOC #1313 typos, formatting, phrasing
prjemian Oct 11, 2023
afd472e
Update contributed_definitions/NXxpcs.nxdl.xml
prjemian Oct 23, 2023
455e63d
DOC #131 only one occurrence
prjemian Oct 23, 2023
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57 changes: 32 additions & 25 deletions contributed_definitions/NXxpcs.nxdl.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -59,7 +59,7 @@
<doc>
**Locally** unique identifier for the experiment (a.k.a. run or scan).

* For bluesky users, this is the run's `"scan_id"`.
* For bluesky users, this is the run's ``"scan_id"``. If ``scan_id`` is not available, use the run's ``uid``.
* For SPEC users, this is the scan number (``SCAN_N``).
</doc>
</field>
Expand Down Expand Up @@ -134,10 +134,10 @@
the data and its axes are self-describing as per NeXus recommendations. However, the data is preferred in one
of the following two formats:

* iterable list of linked files (or keys) for each :math:`g_2` with 1 file (key) per :math:`q`, where `q` is called by the nth roi_map value
* 2D array [#]_ with shape (:math:`g_2`, :math:`q`), where `q` is represented by the nth roi_map value, not the value `q` value
* iterable list of linked files (or keys) for each :math:`g_2` with one file (key) per :math:`q`, where `q` is called by the nth roi_map value
* 2D array [#]_ with shape (:math:`g_2`, :math:`q`), where :math:`q` is represented by the nth roi_map value, not the value :math:`q` value

Note it is expected that "g2" and all quantities following it will be of the same length.
.. note:: It is expected that ``g2`` and all quantities following it will be of the same length.

Other formats are acceptable with sufficient axes description.

Expand All @@ -152,8 +152,8 @@

We encourage the documentation of other formats not represented here.

* one array representing entire data set ("one_array")
* data exchange format with each key representing one ``q`` by its corresponding roi_map value ("data_exchange_keys")
* one array representing entire data set (``"one_array"``)
* data exchange format with each key representing one :math:`q` by its corresponding roi_map value (``"data_exchange_keys"``).
</doc>
<enumeration>
<item value="one_array"/>
Expand Down Expand Up @@ -194,14 +194,14 @@
</field>
<field name="delay_difference" type="NX_INT" units="NX_COUNT" minOccurs="0" maxOccurs="1">
<doc>
delay_difference (also known as delay or lag step)
(Also known as delay or lag step.)

This is quantized difference so that the "step" between two consecutive
frames is one frame (or step ``= dt = 1 frame``)

It is the "quantized" delay time corresponding to the ``g2`` values.

The unit of delay_differences is ``NX_INT`` for units of frames (i.e., integers) preferred,
The unit of delay_differences is ``NX_INT`` (i.e., integers) for units of frames preferred,
refer to :ref:`NXdetector` for conversion to time units.
</doc>
<attribute name="storage_mode" type="NX_CHAR">
Expand All @@ -220,7 +220,7 @@
</doc>
<field name="two_time_corr_func" type="NX_NUMBER" units="NX_ANY" minOccurs="0" maxOccurs="1">
<doc>
two-time correlation of speckle intensity for a given q-bin or roi (represented by the nth roi_map value)
two-time correlation of speckle intensity for a given :math:`q`-bin or roi (represented by the nth roi_map value)

See Fluerasu, Phys Rev E (2007), Eq 1 and Sutton, Optics Express (2003) for an early
description applied to X-ray scattering:
Expand All @@ -231,8 +231,8 @@
the data and its axes are self-describing as per NeXus recommendations. However, the data is preferred in one
of the following two formats:

* iterable list of linked files (or keys) for each q-bin called by the nth roi_map value. data for each bin is a 2D array
* 3D array with shape (frames, frames, q) or (q, frames, frames), where :math:`q` is represented by the nth roi_map value, not the value `q` value
* Iterable list of linked files (or keys) for each :math:`q`-bin called by the nth roi_map value. data for each bin is a 2D array.
* 3D array with shape (frames, frames, :math:`q`) or (q:math:`q`, frames, frames), where :math:`q` is represented by the nth roi_map value, not the :math:`q` value.


The computation of this result can be customized. These customizations can affect subsequently derived results (below). The
Expand All @@ -241,7 +241,7 @@
* Other normalization methods may be applied, but the method will not be specified in this
definition. Some of these normalization methods result in a baseline value of ``0``, not ``1``.

* The various software libraries use different programming languages. Therefore, we need to
* To avoid committing to one specific programming language, we need to
specify the ``time = 0`` origin location of the 2D array for each :math:`q`.

* A method to reduce data storage needs is to only record half of the 2D array by populating
Expand All @@ -251,7 +251,7 @@
</doc>
<attribute name="storage_mode" type="NX_CHAR">
<doc>
storage_mode describes the format of the data to be loaded
The format of the data to be loaded.

We encourage the documention of other formats represented here.
</doc>
Expand All @@ -264,9 +264,9 @@
</attribute>
<attribute name="baseline_reference" type="NX_INT">
<doc>
baseline is the expected value of a full decorrelation
The expected value of a full decorrelation.

The baseline is a constant value added to the functional form of the auto-correlation
The ``baseline_reference`` is a constant value added to the functional form of the auto-correlation
function. This value is required.
</doc>
<enumeration>
Expand All @@ -276,7 +276,7 @@
</attribute>
<attribute name="time_origin_location" type="NX_CHAR">
<doc>
time_origin_location is the location of the origin
Location of the time origin.
</doc>
<enumeration>
<item value="upper_left"/>
Expand All @@ -285,7 +285,7 @@
</attribute>
<attribute name="populated_elements" type="NX_CHAR">
<doc>
populated_elements describe the elements of the 2D array that are populated with data
Describes how elements of the 2D array are populated with data.
</doc>
<enumeration>
<item value="all"/>
Expand All @@ -298,10 +298,10 @@
<doc>
frame weighted average along the diagonal direction in ``two_time_corr_func``

The data format and description should be consistent with that found in "/NXxpcs/entry/data/g2"
The data format and description should be consistent with that found in ``g2``.

* iterable list of linked files for each :math:`g_2` with 1 file per :math:`q`
* 2D array with shape (:math:`g_2`, :math:`q`)
* Iterable list of linked files for each :math:`g_2` with one file per :math:`q`.
* 2D array with shape (:math:`g_2`, :math:`q`).

Note that delay_difference is not included here because it is derived from the shape of
extracted :math:`g_2` because all frames are considered, which is not necessarily the case for :math:`g_2`.
Expand Down Expand Up @@ -507,7 +507,7 @@
roi index array or labeled array

The values of this mask index (or map to) the :math:`Q` value from the
the ``dynamic_q_list`` field. Not that the value of ``0`` represents in-action. XPCS computations
``dynamic_q_list`` field. Not that the value of ``0`` represents in-action. XPCS computations
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Should be Note that the value of ... not Not.....

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are performed on all pixels with a value > 0.

The ``units`` attribute should be set to ``"au"``
Expand All @@ -523,8 +523,8 @@
The only requirement for the list is that it may be iterable. Some expected formats are:

* iterable list of floats (i.e., :math:`Q(r)`)
* iterable list of tuples (i.e., :math:`Q(r)`, :math:`\varphi`), but preferable use the seperate :math:`\varphi` field below
* iterable list of tuples (e.g., (H, K, L); (qx, qy, qz); (horizontal_pixel, vertical_pixel))
* iterable list of tuples (i.e., :math:`Q(r)`, :math:`\varphi`), but preferable use the separate :math:`\varphi` field below
* iterable list of tuples (e.g., :math:`(H, K, L)`; :math:`(q_x, q_y, q_z)`; (horizontal_pixel, vertical_pixel))
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@prjemian I understood recently from CHX, they use a list of arrays for HKL

Is it worth a discussion or should we stick to this (tuples) ?

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@ambarb ambarb Oct 16, 2023 •
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Also, the dynamic_q_list and static_q_list allow for generic implementation of any reciprocal space notation. It seems confusing that there is a phi_list of any kind give the description for q_list.

If phi_lists are a requirement, then we need to develop more guidance on how to use both options to notate any phi dependance to XPCS results (q_list - a list of tuples vs q_list AND phi_list (of which I am unable to describe).

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For some history regarding the origin of q_list: another data type to track Q as a function of roi_map pixel values is to use a python dictionary in which the format is a nested dictionary with key, value pairs of {row_map_pixel_value:reciprocal_space_quantity}. Converting this to an iterable q_list seemed reasonable given that a list was the requested format by others in the NXxpcs origination team.

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Probably the best place for this suggestion as there are concerns on how to make things more clear in terms of the notations used for q (within the q_lists and against the phi_list

To make the usage of q_list absolutely clear and deal with some of the ambiguity in the q-space notation, let's add an attribute with the allowed values of descriptive text.

  • Q(r) --------> attribute value = "radial"
  • Q(r , phi) ---> attribute value = "radial with azimuth" or "radial with phi" or something else @AZjk or @sureshnaps or @qzhang234 can suggest
  • H, K, L -----> attribute value = "hkl"
  • qx, qy, qz --> attribute value = "qxyz"
  • x, y pixels --> attribute value = "pixels"

@AZjk or @sureshnaps or @qzhang234 , for the phi_list can you please describe if this is the same length as your q_list or do you always have one bin for each q-radius? Am I correct in that the Q(r) resolution is limited to your pixel size and that you use the highest resolution possible?

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@padraic-shafer suggestions for attribute names I think are better than what I posted here.

* iterable list of integers (for Nth roi_map value) or strings

This format is chosen because results plotting packages are not common and simple I/O is required by end user.
Expand All @@ -543,15 +543,22 @@
roi index array.

The values of this mask index the :math:`|Q|` value from the
the ``static_q_list`` field.
``static_q_list`` field.

The ``units`` attribute should be set to ``"au"``
indicating arbitrary units.
</doc>
</field>
<field name="static_q_list" type="NX_NUMBER" units="NX_PER_LENGTH" minOccurs="0">
<doc>
1-D list of :math:`|Q|` values, 1 for each roi.
1-D list of :math:`|Q|` values, one for each roi.
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@ambarb ambarb Oct 16, 2023 •
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If we are going to add a static phi list, then do we need to describe how/where these angles are defined? I imagine there is some variabilitiy. Or do we strictly rely on the dynamic_roi_map and the static_roi_map?

@AZjk maybe you can make a separate issue in this repo that describes your system of reference and then reply to the review with a link to said issue if we decide there is a need to include how the phi slices are labled?

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I see that any phi_list is described as
starting with 1 according to the associated roi_map.

I am also a bit confused on how to map phi and q to the same dynamic_roi_map or static_roi_map, unless the q_lists and the phi_lists are of the same length...and in that case it seems redundant

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Should this doc field describe the same options as in its dynamic counterpart?

  • Q(r)
  • Q(r), phi
  • H, K, L
  • qx, qy, qz
  • x, y pixels

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Good catch! You are correct about the inconsistent use of Q and q. In small-angle (which is used together sometimes with XPCS), $Q$ has a different meaning than reciprocal space vector; it represents the total scattered intensity, integrated over all $\vec{q}$. I will suggest a revision as part of this PR. Should that discussion become distracting to the intent of this PR (as stated in the title), I suggest moving such comment and revision to a separate issue.

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@sureshnaps, @AZjk, @qzhang234, @ambarb, @AbbyGi: Can you comment if the options and other documentation for dynamic_q_list should be copied to static_q_list?

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@ambarb ambarb Oct 25, 2023 •
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I believe this very descriptive option of all possible q-notations was left out of static_q_list on purpose because of complexity. Historically, the static_q_list (and now added static_phi_list) are used by the the team at the APS to describe the non-dynamical SAXS.

In the early development phase of NXxpcs, there was a proposal to not include these (the static lists) as part of the NXxpcs definition but to "add on" NXcanSAS. Eventually, we (the scattering community at large) could then contribute new NX definitions for describing the scattering response for GI-SAXS and single crystal diffraction geometries. Ultimately, this is not where compromise was reached in the effort to suggest a NXxpcs definition since none of the participants heavily using XPCS SAXS were using NXcanSAS. The static_q_list was consequently added to the NXxpcs definition.

Why only SAXS? The data types for the non-SAXS could be very much more complicated and perhaps it is easier to just limit this to SAXS. V2 could be to expand this as more non-SAXS progresses and there should probably be a workshop for this.

For instance, HKL is may be addressed best as a 4D array or some X-array that contains each pixel H, K, L, and Intensity. But this is the least useful form. What people would want is the width in user specified directions and integrated intensity overall. Or perhaps others want to include the the data from the rocking curve so one would not just have the average image of the HKL for XPCS but a volume through the q-space region.

As I understood it, this static data have a much finer resolution (but not as high as a beamline built to focus on uSAXS). Therefore, the static_q_list and dyanamic_q_list do not match with the roi_map utilized for the g2 and C2 computations of XPCS. @AZjk please confirm.

I would suggest documenting further that this is limited to SAXS and explaining what the data should be. The open questions would be:

- is it strictly the highest q-resolution possible? if not, do you need an roi_map?
- is it sourced from the average of all XPCS frames or is it a time resolved result?
- what is the difference between the static_q_list and the static_phi_list (same length or is q_list only Q(r)? if the later, how does one know which Q(r) corresponds to the phi_list )?

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Hi @prjemian, per your request, the APS folks have discussed and we think it would be nice to fold phi_list into the q_list. We imagine that there will be a static_q_list and dynamic_q_list, and each list will contain several columns corresponding to, for example, q, phi, qx, qy, qz, h, k, l, so on and so forth.

Each scattering geometry will probably use only a few of these columns, so it would be useful to also come up with some dummy/default values to avoid confusion.

In the future we could further expand this to q_parallel, q_vertical, etc., to include the GIXS geometry as well.

Would this sound like an acceptable plan @padraic-shafer?

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@qzhang234 Thanks for the gathering input from APS folks and sharing the consensus here!

I think that makes sense to fold these into single lists--one for static and one for dynamic. @ambarb: Is this what you were thinking also?

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Since many of those columns (q, phi, qx, qy, qz, h, k, l, etc.) would be empty if we insist that all of them be present...@ambarb had suggested that we could instead add a @storage_mode attribute.

This would be similar to how it is used in the NXxpcs::entry::twotime group, and it could have defined values, such as q_only, q_phi, qxyz, hkl, xy, or whatever makes sense here. Effectively this would act as a tagged union discriminator for the q_lists. I think this sounds useful.

This could be split out into a separate PR, but it seemed relevant to bring it up here. What do others think?

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@ambarb ambarb Oct 30, 2023 •
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Since many of those columns (q, phi, qx, qy, qz, h, k, l, etc.) would be empty if we insist that all of them be present...@ambarb had suggested that we could instead add a @storage_mode attribute.

This would be similar to how it is used in the NXxpcs::entry::twotime group, and it could have defined values, such as q_only, q_phi, qxyz, hkl, xy, or whatever makes sense here. Effectively this would act as a tagged union discriminator for the q_lists. I think this sounds useful.

This could be split out into a separate PR, but it seemed relevant to bring it up here. What do others think?

@padraic-shafer this is what I am thinking. This way we can reduce writing empty fields that do not have to be individually opened to confirm there is NO data in that list. GUI's and other code can just look at the attribute and know what kind of data to expect.

as for as the names go, I like the ones you propose. I would suggest a little change for consistency and not for someone to confuse what xy might be.

q_r, q_phi, q_rphi, q_xyz, hkl, pixel_xy

I suggest q_r, q_phi and redundantlyq_rphi because I do not know if what the APS wants for q_r, q_phi. @qzhang234 are q_r, q_phi the same length? If yes, maybe we can keep them separate and remove q_rphi, but we should probably understand the advantage of this choice from your perspective.

I agree with @qzhang234 about holding off on "q_parallel, q_vertical, etc" until we finalize this and see how this works "in the wild".

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one thing not yet resolved is how the static_q_list is envisioned to be used. I imagine that the list correlates an intensity list so that one may plot I(Q). @qzhang234 can you confirm?

The exact wording in our current NXxpcs definition for static and dynamic q-labels is:

**"Dynamic” represents quantities directly related to XPCS and NXxcps/entry/data and NXxpcs/entry/two_time.

“Static” refers to finer binning used for computation not strictly used for the final XPCS results. Implementation of static binning is left for individual libraries to document. We encourage usage of NXcanSAS to represent standard SAXS results or development of new NeXus definitions for GI-SAXS or other reciprocal space intensity mapping.**

I was wrong, there is a static_roi_map so this part is handled, but I see absolutely no data to plot against the x-variables (static_q_list or static_phi_list). I believe this is because we left it to others to document as the preference was to use NXcanSAS. I am fine with what the community wants to do in this regard (I(Q) fully inside custom NXxpcs versus NXcanSAS), but if the choice is fully inside NXxcps, it seems better to fully document beyond just adding "static_phi_list" and the other discussed changes.

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Since many of those columns (q, phi, qx, qy, qz, h, k, l, etc.) would be empty if we insist that all of them be present...@ambarb had suggested that we could instead add a @storage_mode attribute.

This would be similar to how it is used in the NXxpcs::entry::twotime group, and it could have defined values, such as q_only, q_phi, qxyz, hkl, xy, or whatever makes sense here. Effectively this would act as a tagged union discriminator for the q_lists. I think this sounds useful.

This could be split out into a separate PR, but it seemed relevant to bring it up here. What do others think?

#1314 (comment). should have been in this thread, not where it is at the bottom of this page

</doc>
</field>
<field name="static_phi_list" type="NX_NUMBER" units="NX_PER_LENGTH" minOccurs="0">
<doc>
Array of :math:`\varphi` value for each pixel.

List order is determined by the index value of the associated roi map starting at ``1``.
</doc>
</field>
</group>
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