The book entitled "ARRAY FACTOR DISTORTION ANALYSIS" is developed at National MST Radar Facility an autonomous organization under Department of Space (DOS) in the field of Atmospheric Science & Research, located at Gadanki, Chittoor, AP, India. Readers interested in Antennas design and applications, can find this book their cup of tea. Few antennas when arranged as an array fail to work, results in the thinning of the aperture and the deviation of the excitation from the specified Taylor distribution, resulting in array pattern getting distorted. The ever-increasing demand in the development of software for Aperture Thinned Radiation Pattern as motivated to model the present work. Analysis of Yagi-Uda antenna has been dealt in detail along with the Aperture Thinning, and an user-friendly software is developed to perform the analysis and further to plot the radiation patterns in both principle planes. A detailed analysis is carried out to quantify the degradation in the radiation pattern due to aperture thinning and results are presented. The entire package is developed using the MATLAB. MATLAB was chosen for the numeric computation and visualization of the array pattern.