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Commands TSTooI Documentation TSTooI handles missing data by internally assigning a special numeric value where data are missing. Different input types may have different missing data values but typically - 9 9 9 or a similar extreme value is used. If the output period is specified using setOutputPeriod O ,then extensions to the available time series period are filled with the missing data value. Data flags are supported for some input types. TSTooI displays and output products indicate missing data by blanks, showing the missing data value, or a string (e.g., NC). Filled time series are often required for use in computer models. TSTooI provides a number of features to fill time series data. The data filling process consists of analyzing available data and using the results to estimate missing data values. The estimation process can be simple or complex, resulting in varying degrees of error and statistical characteristics of the final time series. The data analysis uses data available at the time that the fill command is encountered. Consequently if values have been changed since the initial read (e.g., because of layered fill commands), the changed values may impact the analysis. Basic statistical properties of the original data are saved after the initial read to allow use in later fill commands. For example, for monthly time series, the historical monthly averages are computed after the initial read to allow use with a f i l lxi stMonthAverage () command. The overall period that is being filled is controlled by the time series period or analysis period that is specified with fill commands. TSTooI will not automatically extend the period of a filled time series afterthe time series is initially read. Use the setQueryPeriod () and setOutputPeriod ( ) commands to control the time series period. The following table lists the fill techniques that are supported by TSTooI. TSTooI Fill Techniques and Associated Commands Technique Command Typical Use Carry Forward fillCarryForward O See fillRepeat O . This command is bein hased out. Constant fillconstant () Use when missing data can be estimated as a constant. For example, if only the early period of a "regulated" (e.g., reservoir) time series is missing, it may be appropriate to set the values to zero. Monthly total, f i 11DayTSFrom Use to estimate a daily time series by daily pattern 2MonthTSAndlDayTS () applying the pattern of a related daily time series to monthly totals from the related and current time series. For example, use to estimate daily streamflow from monthly total values. Fill from time f i 11 FromTS () Use non-missing values from a time series to series fill missin values in another time series. Commands - 6