A method for rapidly extracting data file samples with an a signal monitor and an automatically adjusted decimation ratio is provided to solve the long-standing problems caused by large data files and small buffers by reducing a large data segment to a smaller, more manageable size automatically so that a lower resolution version of the data segment will be loaded into a fixed-size small buffer in the computer's working space buffer for further data editing. In accordance with the methods of this invention, the segment size will vary during the operation of a means for zooming-in and the decimation ratio is updated and adjusted automatically based on the variation of segment size. The present invention insures that the best resolution of the data segment will be achieved when fitting the varying large size data segment into the fixed small size buffer. The present invention also provides a storage medium encoded with machine-readable computer program code for rapidly extracting data files with an automatically adjusted decimation ratio and an apparatus for rapidly analyzing and editing data files with an automatically adjusted decimation ratio.