A computer-implemented method of analysing periodic data comprising samples indicative of measured values of a periodic signal over time, the method comprising: determining a repeat period T of a periodic waveform in the periodic data; and selecting a value for a time delay τ equal to 1/3 or 2/3 of the determined repeat period, obtaining a three-dimensional vector of delay coordinates for each one of a plurality of samples of the periodic data in a time window, according to Takens' theorem, using the selected value of the time delay τ; transforming each of the three-dimensional vectors into a coordinate system comprising a plurality of predefined vectors including a first vector parallel to the axis x = y = z and two other vectors orthogonal to the first vector, to obtain a projection of an attractor of the periodic data along the first vector; determining a function relating to one or more of a density, shape, orientation, symmetry and size of the attractor projected along said first vector; determining the value of a predefined quantity relating to the attractor from the function; and displaying information representing one or more characteristics of the obtained attractor, wherein the information representing one or more characteristics of the obtained attractor includes the determined value of the predefined quantity, the predefined quantity relates to a width of a band in the projection of the attractor along said first vector; and searching for an irregular event in the periodic data, comprising determining that the periodic data contains an irregular event if the predefined quantity relating to the width of the band in the projection of the attractor along said first vector is indicative of a deviation between the attractor orbit comprising the irregular event and the other attractor orbits. determining a repeat period T of a periodic waveform in the periodic data; and selecting a value for a time delay τ equal to 1/3 or 2/3 of the determined repeat period, obtaining a three-dimensional vector of delay coordinates for each one of a plurality of samples of the periodic data in a time window, according to Takens' theorem, using the selected value of the time delay τ; transforming each of the three-dimensional vectors into a coordinate system comprising a plurality of predefined vectors including a first vector parallel to the axis x = y = z and two other vectors orthogonal to the first vector, to obtain a projection of an attractor of the periodic data along the first vector; determining a function relating to one or more of a density, shape, orientation, symmetry and size of the attractor projected along said first vector; determining the value of a predefined quantity relating to the attractor from the function; and displaying information representing one or more characteristics of the obtained attractor, wherein the information representing one or more characteristics of the obtained attractor includes the determined value of the predefined quantity, the predefined quantity relates to a width of a band in the projection of the attractor along said first vector; and searching for an irregular event in the periodic data, comprising determining that the periodic data contains an irregular event if the predefined quantity relating to the width of the band in the projection of the attractor along said first vector is indicative of a deviation between the attractor orbit comprising the irregular event and the other attractor orbits. <EOS>