How to Use the Square Wave Transform Tool

The objective of this note is to provide guidance on how to use the SWT tool correctly. Its theoretical bases are available at: Skliar, Osvaldo; Monge, Ricardo E.; Gapper, Sherry; Oviedo, Guillermo (2013), arXiv:1309.3719v4 [cs.NA] 7 Oct 2013).

This tool makes it possible to compute, automatically, the SWT of a sequence of samples, n seconds long (n = 1, 2, 3, ..., 10) obtained with a "Sampling frequency" that must be specified. Due to the limited computational power available for the use of this tool, the total number of samples of the sequence of samples (called "Number of samples") must be less than or equal to 3000. These samples may be from an electrophysiological recording, such as an ECG or an EEG. The total duration of the sequence of samples is known as "Time interval (Δt)". For example, if the "Sampling frequency" is 235 Hz and Δt equals four seconds (4 s), the number of samples will be equal to (235 Hz) × (4 s); that is, 940. On the other hand, if the "Sampling frequency" is 160 Hz and Δt equals 10 seconds (10 s), the "Number of samples" will be equal to (160 Hz) × (10 s); that is, 1600.

In "Data", type the sequence of samples to be analyzed. Each sample should be specified using a) a whole number, or b) a whole number followed by a decimal component. In the latter case, separate the whole part from the decimal part by a decimal point (.). Thus, for example, 45.76 will indicate the numeric value of a sample whose whole part is equal to 45 and whose decimal part is equal to 76 (that is, 7 tenths and 6 hundredths). In the decimal part, a maximum number of 14 digits may be specified for each sample. In the sequence of samples typed in "Data", any two consecutive samples must be separated by a comma, a semi-colon or a blank space. Do not use a period to separate any two consecutive samples.

In "Sampling frequency", type the corresponding whole number.

In "Units", type the units in which each sample of the sequence of samples to be analyzed is measured; for example, mV.

In "Time interval (Δt)", select one of the ten available options.

Then, click "Compute SWT" to obtain the SWT for the sequence of samples analyzed.

Information will be provided below on the different types of results which can be obtained.

In "Number of samples", the number of samples in the sequence of samples analyzed will be indicated.

In "Plot of original data", the sequence of samples analyzed will be graphed.

In "Sequence of samples", the numerical values of all the samples in the sequence of samples analyzed will be shown in a table. (Remember that these are the numerical values of the different samples when these samples are expressed in the unit of measurement indicated in "Units".)

In "Sequence of dyads", the sequence of dyads resulting from the analysis will be given.

In "Plot of the Square Wave Transform", the same information as that given in "Sequence of dyads" will be graphed.

The user of this tool may be interested in seeing a graphic representation of an initial portion of that transform in greater detail than that displayed in "Plot of the Square Wave Transform". Suppose that the initial portion chosen from the transform corresponds to frequencies ranging between zero (0) and a particular maximum frequency less than the highest frequency appearing in the corresponding SWT (that is, the one specified by the first element of the last dyad of the previously obtained dyads). In this case, the user can type the value of that maximum frequency in "Maximum frequency", and then click "View partial plot". The respective partial graph of that SWT will then appear in "Partial plot of the Square Wave Transform".

Input data

Sampling frequency: Hz This amount must be equal to the number of samples.
Time interval (Δt):
Number of samples:
Clear inputs

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