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SAP HANA Predictive Analysis Library (PAL)

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3.5.4 Croston's Method<br />

The Croston’s method is a forecast strategy for products with intermittent demand. The Croston’s method<br />

consists of two steps. First, separate exponential smoothing estimates are made of the average size of a<br />

demand. Second, the average interval between demands is calculated. This is then used in a form of the<br />

constant model to predict the future demand.<br />

Initialization<br />

The system checks the first time bucket of the historical values. If it finds a value (not zero), it is set as the Z’s<br />

initial value and X is set to 1. Otherwise, Z is set to 1 and X to 2.<br />

V(t) = Historical value<br />

P(t) = Forecasted value<br />

q = Interval between last two periods with demand<br />

α = Smoothing factor for the estimates<br />

Z = Estimate of demand volume<br />

X = Estimate of intervals between demand<br />

If 1st value ≠ 0<br />

Z(0) = V(1), X(0) = 1<br />

If 1st value = 0<br />

Z(0) = 1, X(0) = 2<br />

Calculation of Forecast Parameters<br />

The forecast is made using a modified constant model. The forecast parameters P and X are determined as<br />

follows:<br />

If V(t) = 0<br />

q = q + 1<br />

Else<br />

Z(t) = Z(t−1) + α[V(t) − Z(t−1)]<br />

X(t) = X(t−1) + α[q − X(t−1)]<br />

Endif<br />

In the last iteration, the parameters Z(f) and X(f) will be delivered for the forecast.<br />

Prerequisites<br />

●<br />

●<br />

No missing or null data in the inputs.<br />

The data is numeric, not categorical.<br />

CROSTON<br />

This is a Croston's method function.<br />

<strong>SAP</strong> <strong>HANA</strong> <strong>Predictive</strong> <strong>Analysis</strong> <strong>Library</strong> (<strong>PAL</strong>)<br />

<strong>PAL</strong> Functions P U B L I C 361

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