Acceleration [Accel]

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The Acceleration function calculates the speed with which the velocity of a field is changing over a given period of time by comparing the current velocity to a previous velocity. Parameters ------------------ Data          The data to use in the calculation. This is typically a field in a data series or a calculated value. Period        The number of bars of data to include in the velocity calculations, not including the current value.                   For example, a period of 3 compares the current 3-bar velocity with that value from 3 bars ago.                   Therefore, the total number of bars included in the calculation is twice the period. Function Value ------------------------ The acceleration is calculated by taking the velocity of the velocity. In other words, it is the speed with which the change in value is changing. The current velocity is calculated by taking the change in value of the data over a given period and dividing it by the size of that period. This is the same as drawing a line through these two points and calculating the slope of that line. The velocity at the beginning of a data series is not defined until there are enough values to fill the given period. Therefore, the acceleration at the beginning of a data series is not defined until there enough values to fill the given period of the velocity that number of bars ago, or a total of twice the period. Close     Vel(Close,2)   Acc(Close,2) --------------------------------------------------------    2    3    4                1    6                1.5    8                2                    0.5          <--- The velocity changed by 1 (2 - 1) over two periods.    9                1.5                 0             <--- The velocity did not change from two periods ago (1.5 vs 1.5). Usage ----------- The velocity is useful for tracking the speed with which data, such as the closing price, is changing. The acceleration, which is the velocity of the velocity, can be used to determine when the velocity is speeding up or slowing down. For example, when the acceleration crosses zero, a reversal may be starting in the direction of the acceleration.