fynance.features.momentums.smstd¶
-
fynance.features.momentums.
smstd
(X, w=None, ddof=0, axis=0, dtype=None)¶ Compute simple moving standard deviation(s) for each X’ series’.
\[smstd^w_t(X) = \sqrt{\frac{1}{w}\sum^{w-1}_{i=0} (X_{t-i} - sma^w_t)^2}\]Parameters: - X : np.ndarray[dtype, ndim=1 or 2]
Elements to compute the moving standard deviation.
- w : int, optional
Size of the lagged window of the moving average, must be positive. If
w is None
orw=0
, thenw=X.shape[axis]
. Default is None.- ddof : int, optional
Means Delta Degrees of Freedom, the divisor used in calculations is
w - ddof
(must be strictly positive), wherew
represents the number of elements in time axis. Default is 0.- axis : {0, 1}, optional
Axis along wich the computation is done. Default is 0.
- dtype : np.dtype, optional
The type of the output array. If dtype is not given, infer the data type from X input.
Returns: - np.ndarray[dtype, ndim=1 or 2]
Simple moving standard deviation of each series.
Examples
>>> X = np.array([60, 100, 80, 120, 160, 80]) >>> smstd(X, w=3, dtype=np.float64) array([ 0. , 20. , 16.32993162, 16.32993162, 32.65986324, 32.65986324]) >>> smstd(X.reshape([6, 1]), w=3, dtype=np.float64).flatten() array([ 0. , 20. , 16.32993162, 16.32993162, 32.65986324, 32.65986324])