1. A method for diagnosing the presence of sleep disorders comprising the steps of: recording a signal representative of respiration from a patient using a logging device which includes a data-acquisition system and a memory, processing the respiratory signal either on-board by the recording device or offline using a computer, dividing the signal into n epochs of equal length, recording events consisting of an hypopnoea followed by an hyperpnoea, detecting for each event its beginning and endpoints, calculating event lengths, and processing each hyperpnoea to derive shape features; wherein the shape features are calculated using singular value decomposition of the hyperpnoea ventilation signal by the steps of extracting the hyperpnoea from the respiratory signal, forming a ventilation signal from the respiratory signal, scaling the ventilation signal to give a vector of values, calculating shape factors from the product of the pseudoinverse of the matrix and the vector of values; and the matrix of orthogonal functions is: M Basis = ( 1 π ⁢ sin ⁡ ( t 2 ) 1 π ⁢ cos ⁡ ( t 2 ) ( 3 ⁢ π ⁢ ⁢ sin ⁡ ( t ) - 8 ⁢ ⁢ cos ⁡ ( t 2 ) ) π ⁢ ⁢ ( 9 ⁢ π 2 - 64 ) ( 3 ⁢ π ⁢ ⁢ cos ⁡ ( t ) - 4 ⁢ ⁢ sin ⁡ ( t 2 ) ) π ⁢ ⁢ ( 9 ⁢ π 2 - 16 ) ) where t is the time base over the hyperpnoea from 0 to 2 pi.