SpecFile as HDF5¶
Introduction to SPEC data files¶
SPEC data files are ASCII files. They contain two general types of line blocks:
- header lines starting with a
#immediately followed by one or more characters identifying the information that follows- data lines
Header lines¶
There are two types of headers. The first type is the file header. File headers always start
with a #F line.
The metadata stored in a file header refers to all the content of the data file, until a
new file header is encountered. There can be more than one file header, but a file with
multiple headers can be treated as a set of multiple SPEC files concatenated into a single one.
File headers are sometimes missing.
A file header contains general information:
#F- file name#E- epoch#D- file time and date#C- First comment (SPEC title, SPEC user)#O- Motor names (separated by at least two blank spaces)
The second type of header is the scan header. A scan header must start with a #S line
and must be preceded by an empty line. This also applies to files without file headers: in
such a case, the file must start with an empty line.
The metadata stored in scan headers refers to a single block of data lines.
A scan header contains the following information:
#S- Mandatory first line showing the scan number and the command that was used to record the scan#D- scan time and date#Q- H, K, L values#P- Motor positions (the corresponding motor names are in the file header#O)#N- Number of data columns in the following data block#L- Column labels (#Nlabels separated by two blank spaces)
Users can also define their own type of header lines in their macros.
There can sometimes be a block of scan header lines after a data block, but before the #S of the next
scan.
Data lines¶
Data blocks are structured as 2D arrays. Each line contains #N values, each value
corresponding to the label with the same position in the #L scan header line.
This implies that each column corresponds to one series of measurements.
A column typically includes motor positions for a given positioner, a timestamp or the measurement of a sensor.
MCA data¶
More recent SPEC files can also comprise multi-channel analyser data, between normal data lines. A multichannel analyser records multiple values per single measurement. This is typically a histogram of number of counts against channels (MCA spectrum), to analyse the energy distribution of a process.
SPEC data files containing MCA data have additional scan header lines:
#@MCA %16C- a spectrum will usually extend over more than one line. This indicates a number of 16 values per line.#@CHANN- contains 4 values:
- the number of channels per spectrum
- the first channel number
- the last channel number
- the increment between two channel numbers (usually 1)
#@CALIB- 3 polynomial calibration values a, b, c. ( i.e. energy = a + b * channel + c * channel ^ 2)#@CTIME- 3 values: preset time, life time, elapsed time
The actual MCA data for a single spectrum usually spans over multiple lines.
A spectrum starts on a new line with @A, and when it spans over multiple lines, all
lines except the last one end by a continuation character \.
Example of SPEC files¶
Example of file header:
#F ./data/binary_mixtures_mca1.100211
#E 1295362398
#D Thu Feb 10 22:43:43 2011
#C id10b User = opid10
#O0 delta gamma omega theta mu sigma sigmat xt
#O1 zt zt1 thd chid rhod xd yd zd
#O2 att0 arcf zf PhiD phigH chigH ygH
#O3 zgH phigV chigV xgV ygV zgV gslithg gslitho
#O4 gslitvo gslitvg slit1T slit1B slit1F slit1R slit1hg slit1ho
#O5 slit1vg slit1vo s0T s0B s0R s0F
#O6 s0hg s0ho s0vg s0vo TRT
#O7 pi trough hv1 mpxthl apdwin apdthl apdhv xcrl2
#O8 thcrl2 zcrl2 picou picod vdrift vmulti vglo vghi
#O9 rien
Example of scan and data block, without MCA:
#S 30 ascan tz3 29.35 29.75 100 0.5
#D Sat Oct 31 15:43:21 1998
#T 0.5 (Seconds)
#G0 0
#G1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
#G2 0
#Q
#P0 40.135381 40.262001 65.6 70 35 -1.83 0 -36.1
#P1 0 0 -1.98 0 0 35.6 86.2 -29.5
#P2 3.0688882 24.893749 295.98749 28 -27.249938
#N 22
#L TZ3 Epoch Seconds If2 If3 If5 If6 If7 If8 I0 It ItdI0 If1dI0 If2dI0 If3dI0 If4dI0 If5dI0 If6dI0 If7dI0 If8dI0 If1 If4
29.35 45246 0.000264 478 302 206 201 209 264 177860 646 0.00363207 0.00468346 0.00268751 0.00169796 0.00146745 0.00115821 0.0011301 0.00117508 0.00148431 833 261
29.353976 45249 0.000295 549 330 219 208 227 295 178021 684 0.00384224 0.00537577 0.00308391 0.00185371 0.00158408 0.00123019 0.0011684 0.00127513 0.00165711 957 282
29.357952 45251 0.000313 604 368 231 215 229 313 178166 686 0.00385034 0.00603931 0.0033901 0.00206549 0.00166698 0.00129654 0.00120674 0.00128532 0.00175679 1076 297
29.362028 45253 0.000333 671 390 237 226 236 333 178387 672 0.00376709 0.00683346 0.00376148 0.00218626 0.00176582 0.00132857 0.00126691 0.00132297 0.00186673 1219 315
29.366004 45256 0.000343 734 419 248 229 236 343 178082 664 0.00372862 0.00765939 0.0041217 0.00235285 0.00185308 0.00139262 0.00128592 0.00132523 0.00192608 1364 330
29.36998 45258 0.00036 847 448 254 229 248 360 178342 668 0.00374561 0.00857342 0.0047493 0.00251203 0.00194009 0.00142423 0.00128405 0.00139059 0.00201859 1529 346
Synthetic example of a file with 3 scans. The last scan includes MCA data.
#F /tmp/sf.dat
#E 1455180875
#D Thu Feb 11 09:54:35 2016
#C imaging User = opid17
#O0 Pslit HGap MRTSlit UP MRTSlit DOWN
#O1 Sslit1 VOff Sslit1 HOff Sslit1 VGap
#o0 pshg mrtu mrtd
#o2 ss1vo ss1ho ss1vg
#S 1 ascan ss1vo -4.55687 -0.556875 40 0.2
#D Thu Feb 11 09:55:20 2016
#T 0.2 (Seconds)
#P0 180.005 -0.66875 0.87125
#P1 14.74255 16.197579 12.238283
#N 3
#L MRTSlit UP second column 3rd_col
-1.23 5.89 8
8.478100E+01 5 1.56
3.14 2.73 -3.14
1.2 2.3 3.4
#S 25 ascan c3th 1.33245 1.52245 40 0.15
#D Sat 2015/03/14 03:53:50
#P0 80.005 -1.66875 1.87125
#P1 4.74255 6.197579 2.238283
#N 4
#L column0 column1 col2 col3
0.0 0.1 0.2 0.3
1.0 1.1 1.2 1.3
2.0 2.1 2.2 2.3
3.0 3.1 3.2 3.3
#S 1 aaaaaa
#D Thu Feb 11 10:00:32 2016
#@MCA %16C
#@CHANN 20 0 19 1
#@CALIB 1.2 2.3 3.4
#@CTIME 123.4 234.5 345.6
#N 2
#L uno duo
1 2
@A 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15\
16 17 18 19
3 4
@A 0 0 2 4 15 10 5 1 0 0 0 0 1 0 0 0\
0 0 0 0
5 6
@A 0 0 0 0 5 7 2 0 0 0 0 0 1 0 0 0\
0 0 0 1
Reading a SpecFile as an HDF5 file¶
Introduction to the spech5 module¶
The silx module silx.io.spech5 can be used to expose SPEC files in a hierarchical tree structure
and access them through an API that mimics the h5py Python library used to read HDF5 files.
The structure exposed is as follows:
/
1.1/
title = "…"
start_time = "…"
instrument/
specfile/
file_header = "…"
scan_header = "…"
positioners/
motor_name = value
…
mca_0/
data = …
calibration = …
channels = …
preset_time = …
elapsed_time = …
live_time = …
mca_1/
…
…
measurement/
colname0 = …
colname1 = …
…
mca_0/
data -> /1.1/instrument/mca_0/data
info -> /1.1/instrument/mca_0/
…
sample/
ub_matrix = …
unit_cell = …
unit_cell_abc = …
unit_cell_alphabetagamma = …
2.1/
…
Scans appear as Groups at the root level. The name of a scan group is
composed of two numbers, the first one being the scan number from the #S
header line, and the second one being the scan order.
If a scan number appears multiple times in a SPEC file, the scan order is incremented by one.
For example, the scan 3.2 designates the second occurence of scan number 3 in a given file.
Data is stored in the measurement subgroup, one dataset per column. The dataset name
is the column label as it appears in the #L header line.
The instrument subgroup contains following subgroups:
specfile- contains two datasets,file_headerandscan_header, containing all header lines as a long string. Lines are delimited by the\ncharacter.positioners- contains one dataset per motor (positioner), including either the single motor position from the#Pheader line or a complete 1D array of positions if the motor names correspond to a data column (i.e. if the motor name from the#Oheader line is identical to a label in the#Lheader line)- one subgroup per MCA analyser/device containing a 2D
dataarray with all spectra recorded by this analyser, as well as datasets for the various MCA metadata (#@header lines). The first dimension of thedataarray corresponds to the number of points and the second one to the spectrum length.
In addition to the data columns, this group contains one subgroup per MCA analyser/device
with links to the data already comprised in instrument/mca_...
spech5 examples¶
Accessing groups and datasets:
from silx.io.spech5 import SpecH5
# Open a SpecFile
sfh5 = SpecH5("test.dat")
# using SpecH5 as a regular group to access scans
scan1group = sfh5["1.1"] # This retrieves scan 1.1
scan1group = sfh5[0] # This retrieves the first scan irrespectively of its number.
instrument_group = scan1group["instrument"]
# alternative: full path access
measurement_group = sfh5["/1.1/measurement"]
# accessing a scan data column by name as a 1D numpy array
data_array = measurement_group["Pslit HGap"]
# accessing all mca-spectra for one MCA device as a 2D array
mca_0_spectra = measurement_group["mca_0/data"]
Files and groups can be treated as iterators, allowing looping through them.
# get all column names (labels) in all scans in a file
for scan_group in SpecH5("test.dat"):
dataset_names = [item.name in scan_group["measurement"] if not
item.name.startswith("mca")]
print("Found labels in scan " + scan_group.name + " :")
print(", ".join(dataset_names))
Note
A SpecH5 object is also returned when one open a SPEC file
through silx.io.open(). See “Getting started with silx.io” for additional information.
