If the shift is some non-integral amount then the data is resampled using a damped sinc function. A shift of 1 corresponds to shifting the data by one data point to the right relative to the fixed scale, ie. The data will fall off one end or another of the output vector as a result of the shift. However, this is not as significant as the edge effect, the convolution is not complete for any data point within 10 points of the edge, so those points cannot be trusted. The missing points in the convolution are assumed to be equal to the end points.
Return value is the shifted array.
The input and output arrays cannot be the same.