Scan Selection

When creating an Hdf5Source, the selection parameter controls which scans are loaded from the HDF5 file. You can specify scans in several ways — from a simple number to flexible text-based expressions.

In all examples below, selection is the value passed as the second argument to Hdf5Source:

from daxs.sources import Hdf5Source

source = Hdf5Source(
    filename="data.h5",
    selection=selection, # see below
    data_mappings={"x": ".1/...", "signal": ".1/..."},
)

Specifying individual scans

Pass a single scan number, or a list of scan numbers:

selection = 42          # load only scan 42
selection = [1, 5, 7]   # load scans 1, 5, and 7

You can also use a NumPy array of integers:

import numpy as np
selection = np.arange(1, 11)   # scans 1 through 10

Using a range

To load a consecutive sequence of scans, write start-end:

selection = "1-50"   # loads scans 1, 2, 3, ..., 50

The range is inclusive on both ends. You can also take every n-th scan by appending :n:

selection = "1-50:2"   # every other scan: 1, 3, 5, ..., 49
selection = "1-50:3"   # every third scan: 1, 4, 7, ..., 49

Loading all scans

Use the keyword "all" to load every scan present in the file:

selection = "all"

Selecting by scan title

Each scan stored in the file has a short text label called a title (for example "ascan sy 0 1 100 1"). You can select scans by writing part of the title as the selection string:

selection = "ascan"       # all scans whose title contains "ascan"
selection = "loopscan"    # all scans whose title contains "loopscan"

The match is case-insensitive. To take every n-th match, append :n:

selection = "ascan:3"    # every third scan among those titled "ascan"

Excluding scans

Add NOT followed by a title fragment or range to remove unwanted scans from the selection:

# All scans 1-100, but skip those titled "dark":
selection = "1-100 NOT dark"

# All "loopscan" scans except those also labeled "reference":
selection = "loopscan NOT reference"

Combining selections

Use AND to add more scans to the current selection:

# Scans 1-20 together with scans 50-70:
selection = "1-20 AND 50-70"

# All "ascan" scans plus all "loopscan" scans:
selection = "ascan AND loopscan"

AND and NOT can be combined freely in a single expression:

selection = "1-200 NOT dark NOT reference"

Note

Exclusions always take priority. If a scan would be both included and excluded, it is excluded. The final list is always sorted in ascending order.

API reference

See Hdf5Source, and in particular the selection parameter, for the full specification.