Summary: The CumFreq program calculates the cumulative (no exceedance,
non-exceedance) frequency and it does probability distribution fitting 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 fits various linear, logarithmic, exponential and
double exponential cumulative frequency distributions, including the normal,
log-normal (lognormal), (log)logistic, Pareto, Weibull, Frechet (Fisher-Tippett type II),
and Gumbel probability distributions, and selects the best fitting distribution using the
method of best fit.
The software is totally free for download. It can be called shareware (freeware) and is in
public domain.
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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 (bands) and return periods (recurrence intervals).
The program also divides the range of data into a number of equal
intervals and calculates an interval frequency distribution or histogram.
The number of intervals is to be given by the user.
Examples are given. More details are found in the program itself.
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Start:
The program starts clicking on CumFreq.Exe.
More details are given in the program itself.
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Acknowledgements:
The program analyses up to 2500 data. In September 2007, Mr. Michael Siek of UNESCO-IHE,
came forward with suggestions for improvement of CumFreq handling a larger data set, up to
2500 data, and for adding a threshold (cutoff value). This has lead to an extended program.
On 3 October 2010 the Cumfreq program for cumulative frequency analysis was expanded with two
additional probabilty distributions (Pareto and Weibull) thanks to suggestions made by Suha Atiyeh.
On 30 July 2011 the CumFreq program was modified with respect to the generalized linear
distribution on account of valuable questions raised by Mr Nur Muhammad.
On 21 December 2011 the CumFreq program was given somewhat improved graphics for very large
databases, and the "calculated verus observed cumulative frequency graph" was added, thanks to a
suggestion by Keith Barnett.
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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
(this one) on the FAQ's page.
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Download:
CumFreq
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