Fuzzy data such as marks, scores, verbal evaluations, imprecise observations, experts' opinions and grey tone pictures, are common. In "Fuzzy Data Analysis" the authors collect their results, aiming to provide the reader with ideas, approaches and methods for processing such data when looking for sub-structures in knowledge basis for an evaluation of functional relationship, for example in order to specify diagnostic of control systems. The modelling presented uses ideas from fuzzy set theory and the suggested methods solve problems usually tackled by data analysis if the data are real numbers. "Fuzzy Data Analysis" is self-contained and is addressed to mathematicians oriented towards applications and to practitioners in any field of application who have some background in mathematics and statistics.