SMOOTHING... ⌘F (Active channel
only) Performs nearest-neighbor smoothing with a choice of 3, 5, 7, 9, 11,
15, 19, 25, 35, or 51- point smoothing intervals with one or more
repetitions (the default is 1). The smoothing interval is the number of
adjacent cases averaged for each smoothed point. For example, 5-point smoothing
includes the data point itself, the two immediately earlier points, and
the two immediately later points in the averaged value.
The program makes a memory copy of the channel
and uses that as its data source (this insures that within a given smoothing
iteration, previously smoothed data are not part of the calculations).
When smoothing is complete, the channel is redrawn. If a block has
been selected, you can smooth either all the data or just within the block.
You can also smooth conditionally, changing only those data within a certain
range (i.e., greater than or less than user- specified values). If
the file contains less than 40 channels, you can copy the active channel
to a new channel before smoothing.
The example at right shows 19-sample smoothing to be repeated over six
cycles. Notice that the indicated smoothing interval (calculated from
the sample interval and the averaging interval of 19 samples) is 28.5 seconds.
Conditional smoothing is selected, and smoothing will be applied only to
data points will values less than 12.5.
Smoothing can be repeated as often as necessary, but be very careful
that you do not obliterate useful information from the data. For example,
smoothing a high-frequency waveform may result in a substantial decrease
in the peak amplitude, although this should not affect frequency calculations.
Remember that you can undo only the last smoothing operation performed.
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