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TSTool Documentation Commands <br />TSTool handles missing data by internally assigning a special numeric value where data are missing. <br />Different input types may have different missing data values but typically - 9 9 9, a similar extreme value, <br />or NaN (not a number) is used. If the output period is specified using Set Output Period(), then <br />extensions to the available time series period are filled with the missing data value. Data flags are <br />supported for some input types. TSTool displays and output products indicate missing data by blanks, <br />showing the missing data value, or a string (e.g., NC). <br />Filled time series are often required for use in computer models. TSTool provides a number of features <br />to fill time series data. The data filling process consists of analyzing available data and using the results <br />to estimate missing data values. The estimation process can be simple or complex, resulting in varying <br />degrees of error and statistical characteristics of the final time series. The data analysis uses data that are <br />available at the time that the fill command is encountered. Consequently if values have been changed <br />since the initial read (e.g., because of layered fill commands), the changed values may impact the <br />analysis. Basic statistical properties of the original data are saved after the initial read to allow use in later <br />fill commands. For example, for monthly time series, the historical monthly averages are computed after <br />the initial read to allow use with a FillxistMonthAverage ( ) command. <br />The overall period that is being filled is controlled by the time series period or analysis period that is <br />specified with fill commands. TSTool will not automatically extend the period of a filled time series <br />afterthe time series is initially read. Use the SetlnputPeriod ( ) and SetOutputPeriod ( ) <br />commands to control the time series period. <br />The following table lists the fill techniques that are supported by TSTool. <br />TSTool Fill Techniques and Associated Commands <br />Technique <br />Command <br />Typical Use <br />Constant <br />FillConstant O <br />Use when missing data can be estimated as a <br />constant. For example, if only the early <br />period of a "regulated" (e.g., reservoir) time <br />series is missing, it may be appropriate to set <br />the values to zero. <br />Monthly total, <br />FillDayTSFrom <br />Use to estimate a daily time series by <br />daily pattern <br />2McnthTSAnd1DayTS () <br />applying the pattern of a related daily time <br />series to monthly totals from the related and <br />current time series. For example, use to <br />estimate daily streamflow from monthly <br />total values. <br />Fill from time <br />FillFromTS () <br />Use non - missing values from a time series to <br />series <br />fill missing values in another time series. <br />Historic <br />FillHistMonthAverage () <br />Use with monthly time series to estimate <br />Monthly <br />missing monthly values as the average of <br />Average <br />historic monthly values. For example, if <br />applied to monthly precipitation data, a <br />missing July value would be set to the <br />average of observed July precipitation values <br />(zero is an observation). <br />61 Commands - 7 <br />