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Contents of check for Mann-Kendall Check
Overwrites the flag of the timeseries with unreliable or doubtful when there are at least ten observations and the Mann-Kendall detects a trend but the value does not follow the trend for the specified confidence balance. This check uses tiedValues and sameYearValues for the calculation.
The purpose of this check is to test for trends in each of the input time series. Once a trend is detected the check will alter the flags of the timeseries concerned to the specified output flag and the specified log message will be generated. One of the strengths of the Mann-Kendall check is that it can also be used when there are lots of missing values. If there are less than 10 non-missing values, the test will be skipped. During the check, the threshold criteria for the check are first sorted so that the most severe log message is processed first. When the log message is generated the less serious log message will not be generated. The trend analysis is done using the formula below. Every value is compared with all the other values in the series and the signs of the differences are counted as 1 or -1.
General information on Mann-Kendall trend test
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the number of multiple data in the qth time period
Z statistic
Z=
, if S > 0,
- Z = 0
, if S = 0
, if S < 0,
Slope
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