Computing features on Signals#

This section describes the signal computing features available in DataLab.

See also

Operations on Signals for more information on operations that can be performed on signals, or Processing Signals for information on processing features on signals.


Screenshot of the “Computing” menu.#

When the “Signal Panel” is selected, the menus and toolbars are updated to provide signal-related actions.

The “Computing” menu allows you to perform various computations on the selected signals, such as statistics, full width at half-maximum, or full width at 1/e².


In DataLab vocabulary, a “computing” is a feature that computes a scalar result from a signal. This result is stored as metadata, and thus attached to signal. This is different from a “processing” which creates a new signal from an existing one.

Edit regions of interest#

Open a dialog box to setup multiple Region Of Interests (ROI). ROI are stored as metadata, and thus attached to signal.

ROI definition dialog is exactly the same as ROI extraction (see above): the ROI is defined by moving the position and adjusting the width of an horizontal range.


A signal with an ROI.#

Remove regions of interest#

Remove all defined ROI for selected object(s).


Compute statistics on selected signal and show a summary table.


Example of statistical summary table: each row is associated to an ROI (the first row gives the statistics for the whole data).#


Compute histogram of selected signal and show it.

Parameters are:




Number of bins

Lower limit

Lower limit of the histogram

Upper limit

Upper limit of the histogram


Example of histogram.#

Full width at half-maximum#

Compute the Full Width at Half-Maximum (FWHM) of selected signal, using one of the following methods:




Find the zero-crossings of the signal after having centered its amplitude around zero


Fit data to a Gaussian model using least-square method


Fit data to a Lorentzian model using least-square method


Fit data to a Voigt model using least-square method


The computed result is displayed as an annotated segment.#

Full width at 1/e²#

Fit data to a Gaussian model using least-square method. Then, compute the full width at 1/e².


Computed scalar results are systematically stored as metadata. Metadata is attached to signal and serialized with it when exporting current session in a HDF5 file.

X values at min/max#

Compute the X values at minimum and maximum of selected signal.

Peak detection#

Create a new signal from semi-automatic peak detection of each selected signal.


Peak detection dialog: threshold is adjustable by moving the horizontal marker, peaks are detected automatically (see vertical markers with labels indicating peak position)#

Sampling rate and period#

Compute the sampling rate and period of selected signal.


This feature assumes that the X values are regularly spaced.

Dynamic parameters#

Compute the following dynamic parameters on selected signal:




Frequency (sinusoidal fit)


Effective Number Of Bits


Signal-to-Noise Ratio


Signal-to-Noise And Distortion Ratio


Total Harmonic Distortion


Spurious-Free Dynamic Range

Bandwidth at -3 dB#

Assuming the signal is a filter response, compute the bandwidth at -3 dB by finding the frequency range where the signal is above -3 dB.


This feature assumes that the signal is a filter response, already expressed in dB.


Compute the contrast of selected signal.

The contrast is defined as the ratio of the difference and the sum of the maximum and minimum values:

\[\text{Contrast} = \dfrac{\text{max}(y) - \text{min}(y)}{\text{max}(y) + \text{min}(y)}\]


This feature assumes that the signal is a profile from an image, where the contrast is meaningful. This justifies the optical definition of contrast.

Show results#

Show the results of all computations performed on the selected signals. This shows the same table as the one shown after having performed a computation.

Plot results#

Plot the results of computations performed on the selected signals, with user-defined X and Y axes (e.g. plot the FWHM as a function of the signal index).