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In statistics and data analysis the application software CumFreq is a free and user-friendly tool for cumulative frequency analysis of a single variable and for probability distribution fitting. Originally the method was developed for the analysis of hydrological measurements of spatially varying magnitudes (e.g. hydraulic conductivity of the soil) and of magnitudes varying in time (e.g. rainfall, river discharge) to find their return periods. However, it can be used for many other types of phenomena, including those that contain negative values. ==Software features== CumFreq uses the plotting position approach to estimate the ''cumulative frequency'' of each of the observed magnitudes in a data series of the variable.〔''Frequency and Regression Analysis''. Chapter 6 in: H.P.Ritzema (ed., 1994), ''Drainage Principles and Applications'', Publ. 16, pp. 175–224, International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands. ISBN 90-70754-33-9 . Free download as PDF from : (ILRI website ) or from : ()〕 The computer program allows determination of the best fitting probability distribution. Alternatively it provides the user with the option to select the probability distribution to be fitted. The following probability distributions are included: normal, lognormal, logistic, loglogistic, exponential, Cauchy, Fréchet, Gumbel, Pareto, Weibull and others. Another characteristic of CumFreq is that it provides the option to use two different probability distributions, one for the lower data range, and one for the higher. The ranges are separated by a break-point. The use of discontinuous probability distributions can be useful when the data of the phenomenon studied were obtained under different conditions. During the input phase, the user can select the number of intervals needed to determine the histogram. He may also define a threshold to obtain a truncated distribution. The output section provides a calculator to facilitate interpolation and extrapolation. Further it gives the option to see the Q–Q plot in terms of calculated and observed cumulative frequencies. ILRI 〔''Drainage research in farmers' fields: analysis of data'', 2002. Contribution to the project “Liquid Gold” of the International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands. ()〕 provides examples of application to magnitudes like crop yield, watertable depth, soil salinity, hydraulic conductivity, rainfall, and river discharge. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「CumFreq」の詳細全文を読む スポンサード リンク
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