Using the Statistics tab of the Results Manager, you can carry out several types of statistical analyses on scenario results. For simplicity, they can be categorised into two groups:
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| Note: Statistics may be are affected by the chart type (selected in the Chart tab) and any transforms applied to result(s). See Data Manipulation for more details. |
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If a single result is selected from the left-hand tree menu of the Results Manager window, the statistics tab will show univariate statistics (Figure #1). For multiple results in a custom chartschart, the statistics tab will have two options: univariate and bivariate statistics (Figure #2).
Figure #1. Univariate statistics (single result)
Figure 2. Univariate statistics (multiple results), yearly summary
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You can view univariate statistics for a single result (as shown in Figure #1) or for each individual result when multiple results are combined (Figure #2). A brief description of each univariate statistic is given in Table 1.
Table 1. Univariate Statistics
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Statistic
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Definition
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Example for
[-9999, 0, 1, 3, 5, 9, 9]
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Minimum
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Minimum value in the time series.
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0
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Maximum
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Maximum value in the time series.
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9
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Number of Values
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The number of values in the time series, not including nulls.
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6
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Number of Nulls
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The number of nulls, either missing values or values entered as -9999. These values are ignored in all other univariate statistics.
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1
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Total
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The sum of all values in the time series.
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27
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Mean
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The sum of all values in the time series divided by the number of values,
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5
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Median
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The middle value in the sorted list of all values in a time series. For n values, the middle value is 
. When n is even, the median is the mean of the two middle values.
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4
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Standard Deviation
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How widely values in the time series vary from the mean. See Standard Deviation.
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3.89 (to 2 decimal places)
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Skew
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The skewness of the distribution of values in the time series. See Skew.
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0.23 (to 2 decimal places).
For univariate statistics for a shows both univariate comparison and bivariate statistics for two of the results in the chart.
For statistics for a single result, you can:
- Choose the period type (Table 1) used to calculate the statistics from the drop down menu;
- Change the Water Year Start from from the default date (the default is set in Project Options);
- View the result used to calculate the statistics under under Data; and you're data
- View the statistics themselves.
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For univariate statistics for of multiple results, the Univariate Comparison tab shows a comparison between two of the results in your custom chart. You can:
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you can also:
- Toggle on or off two Statistics Statistics Options for for how the two results are compared (Table 3);
- View and change the result used as the X Data (reference) and the the Y Data for for statistic calculations (in Figure #2, this is Downstream Flow Volume); and
- View the statistics themselvesSelect to view either Univariate Comparison or Bivariate statistics for the two results.
Table
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1. Basic statistical analysis, period types
| Period type | Description |
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| Total | Provides statistics for the entire run. This is the default period. |
| Yearly summary | Provides annual statistics, with one row for each year in the run. |
| Monthly summary | Provides monthly statistics by combining the data for each month, regardless of the year. There are 12 rows, one for each calendar month. For example, the January row displays statistics calculated from data for every January for all years in the run. |
| MonthxYear summary | Provides monthly statistics by month and year, with one row for each month-year pair in the run. For example, December 1999, January 2000, February 2000 ... etc. |
Table
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2. Multiple results, parameters
| Parameter | Description | Default |
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| Calculate using overlapping data only |
| Enabled |
| Set all N/A to 0 |
| Disabled |
Figure 2. Univariate statistics (multiple results), yearly summary
Naming conventions of difference, double mass and scatter statistics.
If you have a custom chart with a chart type of difference, double mass or scatter, then the following naming conventions are used in the statistics tab (Figure 3):
- Each result in the custom chart is given a letter. This is shown in a Legend in the bottom left of the statistics tab.
- The series used as a reference in the chart is always given letter A. To change the reference series, go to the Chart view then select Chart Settings » Charts and modify Chart Type Reference Series.
- Under X Data (Reference) and Y (Data), the results are listed using the letters to represent each result.
For example, in Figure 3, A - B corresponds to the difference between Crab Creek's Downstream flow volume (result A) and Fish Creek's Downstream Flow Volume (result B).
Figure 3. Statistics, Difference Chart Type
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You can view univariate statistics for a single result (as shown in Figure #1) or for each individual result when multiple results are combined (Figure #2). A brief description of each univariate statistic is given in Table 1.
Table 1. Univariate Statistics
Statistic | Definition | Example for |
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Minimum | Minimum value in the time series. | 0 |
Maximum | Maximum value in the time series. | 9 |
Number of Values | The number of values in the time series, not including nulls. | 6 |
Number of Nulls | The number of nulls, either missing values or values entered as -9999. These values are ignored in all other univariate statistics. | 1 |
Total | The sum of all values in the time series. | 27 |
Mean | The sum of all values in the time series divided by the number of values, | 5 |
Median | The middle value in the sorted list of all values in a time series. For n values, the middle value is | 4 |
Standard Deviation | How widely values in the time series vary from the mean. See Standard Deviation. | 3.89 (to 2 decimal places) |
Skew | The skewness of the distribution of values in the time series. See Skew. | 0.23 (to 2 decimal places). |
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When two or more results are in a custom chart, a set of bivariate statistics is automatically generated and can be viewed on the Bivariate Statistics tab (Figure #3#4). A brief description of each bivariate statistic is given in Table 4, where:
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Statistic | Definition | Range |
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Values Used | The number of time steps for which there are complete data pairs ie. both the X data and Y data time series have values. These pairs are used to calculate the bivariate statistics. Time steps where either series has missing values are not used. | 0 to +∞ |
Values not used from X | The number of time steps in the X Data series that are not used in bivariate statistics calculations because either the X data or the Y data have missing values for those time steps. | 0 to +∞ |
Values not used for Y | The number of time steps in the Y Data series that are not used in bivariate statistics calculations because either the X data or the Y data have missing values for those time steps. | 0 to +∞ |
Pearson's Correlation (r) | Pearson's correlation coefficient measures the linear correlation between two variables. Pearson's correlation coefficient is symmetric, meaning that the value will be the same regardless of which time series is defined as X data (reference) and which as the Y data. See Pearson's Correlation Coefficient. | -1 to 1 |
Volume Bias (%) | Relative bias expressed as a percentage. See Relative Bias. | 0 to 100 |
Minimise Absolute Bias | The absolute value of the relative bias. See Relative Bias. | 0 to +∞ |
| NSE Daily | The NSE for using a daily time step. See Nash-Sutcliffe Efficiency. | -∞ to 1 |
NSE Daily & Bias Penalty | The difference between NSE daily and the Bias Penalty. See NSE Daily & Bias Penalty. | -∞ to 1 |
NSE Daily & Flow Duration | Combines the NSE Daily and Flow Duration using a user-defined weighting factor. See NSE Daily & Flow Duration. | -∞ to 1 |
| NSE Daily & log Flow Duration | Combines the NSE Daily and log Flow Duration using a user-defined weighting factor. Log flow duration is the NSE of flow duration of the logarithm of data, calculated using a daily time step. See NSE Daily & log Flow Duration. | -∞ to 1 |
| NSE Log Daily | The NSE of the logarithm of data, using a daily time step. See NSE of Log Data. | -∞ to 1 |
| NSE Log Daily & Bias Penalty | The difference between NSE Log daily and the Bias Penalty. See NSE Log Daily & Bias Penalty. | -∞ to 1 |
| NSE Monthly | The NSE using a monthly time step. See Nash-Sutcliffe Efficiency. | -∞ to 1 |
| NSE Monthly & Bias Penalty | The difference between NSE monthly and the Bias Penalty. See NSE Monthly & Bias Penalty. | -∞ to 1 |
| Square-root Daily, Exceedance and Bias | Combines three terms, the sum of errors on power transformed flow, the same sum on sorted flow values, and the relative simulation bias. See Sum of Daily Flows, Daily Exceedance (Flow Duration) Curve and Bias. | 0 to +∞ |
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#4. Bivariate statistics, Total period
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where xi is the ith value of the flow series x, xt is the user-defined threshold value for x, yj is the jth value of the flow series y, and yt is the user-defined threshold for y. This statistic can be used to calculate several useful parameters such as Volumetric runoff coefficients and Stream Erosion Index(SEI). To calculate SEI, it is necessary to know the flow threshold (critical flow) below which no erosion is expected to occur within a waterway. This threshold can be represented (EarthTech, 2005) as a percentage of the pre‐development two-year ARI peak flow at the location in question. The percentage depends on the stream bed material and usually varies between 10 – 50%. The pre-development two-year ARI peak discharge can be estimated using flood frequency analysis or the rational method as described in Australian Rainfall and Runoff (Pilgrim, D.H., 2001). Flux Files containing the pre- and post-development outflows can be generated from MUSIC model run. SEI can be calculated by creating a custom chart in Results Manager where X data is the post-development outflow, Y data is the pre-development outflow, and both the X data and Y data threshold values are manually set to the value of critical flow using the appropriated fields next to the volumetric ratio. Although Results Manager can calculate a volumetric ratio for any two data series, currently this statistic supports data expressed as either volume (eg. ML) or rate (eg. m3/s). |
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Figure #4 #5 shows annual descriptive statistics for a single result:
- The upper left pane shows the overall statistical data;
- The upper right pane allows you to select the relevant run/s; and
- The table at the bottom shows the resulting statistical data on an annual basis.
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#5. Annual descriptive statistics
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To calculate mass balance, right click on a result set and select Statistics » New Mass Balance from the contextual menu (Figure #5#6). A new mass balance statistic will be created and listed under Statistics in the Custom Chart and Statistics pane, and the mass balance tool will be shown in the central workspace (Figure #5#6), where:
- The lower right pane allows you to select the result set(s) and time period used to calculate the mass balance;
The upper right pane includes four tabs: Storage Start, Inflow, Outflows, Storage End; which will accept results listed in the upper left pane;
Info icon false Note: The Is Grouped checkbox relates to the mass balance report exported from the Results Manager using Export To Excel. If this box is unchecked, the result will be reported as its own separate total, otherwise a single grouped total will be given for each tab. - The upper left pane lists the results from the selected result sets(s); right click on a result to add it to one of the four tabs in the upper right panel; and
- The lower left pane is the mass balance check, which will calculate the flow from the four tabs in the upper right panel.
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Note: If a result is selected for use in the mass balance, and then a result set is selected that does not contain that result, a value of zero will be assumed for the missing result. |
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#6. Mass balance