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I have trouble understanding parameters lx and ly (the number of lagged values affecting the current value of x/y) and results of the calculation for time series with different lags.
Suppose I have two identical time series v1 and v2 (a sine wave) but v2 is lagged by a single time point:
require(RTransferEntropy)
n.shift = 1 # the number of points by which v2 is delayed with respect to v1
vt = seq(0, 10*pi, 0.1)
v1 = sin(vt)
v2 = vecShift(v1, in.n = n.shift, in.circle = T)
The vecShift function is available here. It shifts a vector by a user-defined number of points. Here, I'm using periodic boundary conditions.
The TE calculation gives me:
RTransferEntropy::transfer_entropy(v1, v2, lx = n.shift, ly = n.shift)
Direction TE Eff. TE Std.Err. p-value sig
-----------------------------------------------------------
X->Y 0.3217 0.3080 0.0067 0.0000 ***
Y->X 0.0234 0.0092 0.0073 0.1000
Now, the same sine wave is lagged by 10 points:
n.shift = 10
v2 = vecShift(v1, in.n = n.shift, in.circle = T)
RTransferEntropy::transfer_entropy(v1, v2, lx = n.shift, ly = n.shift)
Direction TE Eff. TE Std.Err. p-value sig
-----------------------------------------------------------
X->Y 0.2415 0.1129 0.0292 0.0000 ***
Y->X 0.0355 0.0000 0.0285 1.0000
What I don't get is why TE is smaller than in the first calculation. I'm still comparing the same time series. The lag is larger but from what I understand I'm also calculating TE at a longer lag (by setting lx and ly parameters).
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