Compute elementtoelement difference along specified dimension of input
DSP System Toolbox / Math Functions / Math Operations
The Difference block computes the difference between adjacent elements in rows, columns, or a specified dimension of the input array u. You can configure the block to compute the difference only within the current input, or across consecutive inputs (running difference).
Data Types 

Direct Feedthrough 

Multidimensional Signals 

VariableSize Signals 

ZeroCrossing Detection 
