SPECPR Users’ Manual Page 8-f2.1 F2: Shift Channels Left or Right Alias: shift Special function f2 shifts data left or right an integer or fractional number of channels. A data set is required and errors can be included. Fractional shifts are done by linear interpolation. When the routine has been entered, type: the number of channels to shift, or e to soft exit, or x to hard exit. A positive number (integer or real) indicates a shift right and a negative number left. If X is the number of channels to shift, the value of X is split into the integer part (n) and the fractional part (XN). First, the integer part is shifted Di+n = Di (eqn 8.f2.1) where Di is each data channel in the spectrum. Next, the fractional part is interpolated XN’ > 0.0; Di = Di+1 - Di * XN’ + Di (eqn 8.f2.2) XN’ < 0.0; Di = Di - Di-1 * XN’ + Di (eqn 8.f2.3) where XN’ = -1.0 * XN. Data channels not in the shifted region are set to zero. The errors to the data are shifted in a similar manner. Before June 24, 1979, there was a slight error in the program (XN’ = XN) making the fractional shift appear to go in a different direction than the integer part shift. The history has been modified to signal this new change: Old history (X = + 2.5 operation on WDG536 file 238): "F2: wdg536 FILE 238 shift right 2.5 channels" New History: "F2: wdg536 r 238 shift right (+) 2.5 channels". The subtle change is the sign (+ or -) in parentheses signifying the direction of the shift (very early version may have had the words in upper case).