# DDJ Histogram

The Data-Dependent Jitter (DDJ) histogram displays the jitter that is correlated to the data pattern. The graph's horizontal axis indicates negative (-) time for samples that occur earlier than expected and positive (+) time for samples that occur later than expected. When the source waveform is a clock-type signal, the mean of the DDJ histogram is always equal to zero. When the source waveform is a data-type signal, then mean of the histogram of DDJ from all edges is always equal to zero.