Compression

LTspice compresses the raw data files as they are generated. A compressed file can be 50 times smaller than the un-compressed one. This is a lossy compression. This pane of the control panel allows you to control how lossy the compression runs.

Window Size(No. of Points): Maximum number of points that can be compressed into two end points. Set to zero to turn off waveform compression.

Relative Tolerance: The relative error allowed between the compressed data and the uncompressed data.

Absolute Voltage tolerance[V]: The voltage error allowed by the compression algorithm.

Absolute Current tolerance[A]: The current error allowed be the compression algorithm.

These compression settings are not remembered between program invocations to encourage use of the defaults. They are available on the control panel for diagnostic purposes. The tolerances and window size can be specified with option parameters plotreltol, plotvntol, plotabstol and plotwinsize in .option statements placed as SPICE directives on the schematic.

You will probably want to turn of compression when using .four statements or doing FFT's in post analysis of your data with the SPICE directive:

.options plotwinsize=0