Differentiation is dy/dt, where dt is the sampling distance (1/rate), and dy is (y1-y0). It is computed continually - the output signal is the slope as it changes over time.
To change the computation, you can use a Relay to snapshot samples based on a trigger or other timing signal, or, you can use Averaging to do the computation (average over 3000 samples, at 10 s/sec, would give you points every 5 minutes).
I also looked at Linear Regression, where the block size was modified (I used the Data Window module) to make the block be 3000 samples. The output value matched the Average slope, and matched the cursor values, too. I was using a Sine wave, to guarantee that the slope changed over time.
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