Summary: The CumFreq program calculates the cumulative (non-exceedance)
frequency and probability distribution of data series, e.g. crop production, soil
properties, salinity, depth to watertable (water-table), rainfall, river and drain
discharge, groundwater (ground-water) and river level, hydraulic conductivity and
soil permeability for water.
The computer program tests various linear, logarithmic, exponential and
double exponential cumulative frequency functions, including the normal,
log-normal (lognormal), and Gumbel distributions, and selects the best
fitting function (method of best fit).
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Details:
When the mathematical model program detects a discontinuity in the function,
it gives the user the choice to introduce a breakpoint (break-point) or threshold
value, yielding a segmented or discontinuous frequency and probability distribution.
The resulting probability distribution is accompanied by 90% confidence
limits and belts and return periods (recurrence intervals). Examples are given.
The program also divides the range of data into a number of equal
intervals and calculates an interval frequency distribution.
The number of intervals is to be given by the user.
On 25 February 2005 the program was updated to include an option to select
specific distributions: Normal, Log-Normal, Gumbel, and on 9 December 2005
return periods were added.
More details are given in the program itself.
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Start:
The program starts clicking on CumFreqW.Exe.
More details are given in the program itself.
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Acknowledgement:
The program analyses up to 1200 data. In September 2007, Mr. Michael Siek of UNESCO-IHE,
came forward with suggestions for improvement of CumFreqW handling a larger data set, up to
2500 data, and for adding a threshold (cutoff value). This has lead to an extended program.
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Documentation:
A lecture note ("Data Analysis") on statistical analysis with examples of CumFreq
applications is found on the articles page.
The principles of frequency analysis can be found in a lecture note on the
FAQ's page.
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Download:
CumFreqW
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