Analysis of data from periodical signals: the movement of the beans leaf.- A set of numerical programs to analyze data from periodical signals from bean's leaf is proposed. The methods used are: polynomial trend analysis, periodogram, variance spectrum, power spectrum, cosinusoïdal regression with m-components, cosinor and complex demodulation. They are illustrated using data collected from experiments proceeded from the circadian movement of the beans leaf. The rotation of the leaf is measured with a lever. The installation allows to estimate angles with an absolute precision value of 0.5°; moreover, the rhythm could be monitored continuously in any kind of photo- or thermoperiodic treatment. In constant conditions (22.5°, 4500 lux) the periodicity of the movement is 26.4 hours.