Difference, Cumulative, Normalize

The Difference, Cumulative, Normalize option in the Time menu or the Time toolbar can difference the data with adjustable order and lag, compute various cumulatives, and normalize for unit area, unit power, unit standard deviation, and zero mean.

This option presents an AutoSignal graph displaying the input and detrended data.

Process

The procedure can generate normalized Data. The Difference item specifies that differencing, the discrete analog of differentiation, is to take place. The Cumulative option specifies that a cumulative, the discrete analog of integration, will be generated.

Diff. Options

The difference options are only available if Difference is checked. The Order field specifies the order of the differencing. Most often first order differencing is used. This is the equivalent of taking the first derivative of continuous data. Orders through 4 are supported. The Lag field specifies the delta of the differencing. Usually a lag 1 is used to produce the difference from adjacent elements. A lag of 12 is used sometimes to seasonally adjust monthly data. Similarly, a lag of 4 can be used to seasonally adjust quarterly data.

If dY is selected, the differencing is based only on the Y-values in the data set. If dY/dX is selected, the differencing is processed like a derivative generating a discrete rate value.

Cum. Options

The cumulative options are only available if Cumulative is checked. The Simple option generates a cumulative by basic addition. The Area option uses the x spacing to produce an area cumulative. The Power option uses the x-spacing to produce a TISA (time-integral squared amplitude) cumulative power data series. For oscillatory data, the cumulative power curve will be continuously increasing.

Normalize

The normalizations apply to all processing options. No normalization is made if None is checked. The data can be normalized to Unit Area, Unit Power (TISA), or Unit SD (standard deviation). If the Zero Mean box is also checked, the mean of the resulting series will be zero.

Data Count

If differencing is done, the output data count will be reduced. The input and output counts are displayed in the nIn and nOut informational fields.

List

The List Data option lists the index, x-values, and the processed data. The listing uses the AutoSignal text viewer facility.

Copy

The Copy Data to Clipboard option copies the x values and processed data to the clipboard. Formats include full precision binary (for spreadsheets such as Excel) and ASCII (for pasting into text editors).

Save

The Save Data to Disk option writes the x-values and processed data to a supported file format. These formats include ASCII, Excel 97, Excel 95, Lotus WK3, Lotus WK1, SPSS, or Systat.

Production Facility

The AutoSignal Automation facility allows unattended processing of large numbers of data sets. The data sets can be consolidated in an Excel file or acquired using a DLL. The graphs can be exported to a MS Word RTF file, while the processed data can be exported to an Excel 95 or Excel 97 file.

If an Automation Session is in progress, the Reset button can be used to terminate the automated processing.

When exiting this procedure with the OK button, an option will be presented to update AutoSignal's main data table with the processed data.