Curve fitting made easy!
Some of the code were taken from ShinyCFA
The frequency distribution(s) are fitted using L-moments method from R package lmom by J. R. M. Hosking. L-moments of the sample data are calculated. Distribution parameters are then estimated from the calculated L-moments.
Return periods of the quantile values are calculated using the Weibull formula: Tr = (N+1) / m where N is the sample size and m is the rank. Probability of Non-exceedance is the inverse of return period: P = 1 / Tr. Frequency distribution plots' x-axis has been transformed into probabilistic scale: η = −log(−log(P)) = −log[−log(1 − 1/Tr)] where η is the reduced variate.
Further readings:
- Hosking, J., & Wallis, J. (1997). Regional Frequency Analysis: An Approach Based on L-Moments. Cambridge: Cambridge University Press. doi:10.1017/CBO9780511529443
- Makkonen, L. (2006). Plotting Positions in Extreme Value Analysis, Journal of Applied Meteorology and Climatology, 45(2), 334-340. doi:10.1175/JAM2349.1
The file upload takes either CSV or Excel formats. In either case, only the first column will be recognized. The imported file should NOT have header.
Although the original intend of the app (sister app ShinyCFA) was to fit streamflows, this app can be used to fit just about anything (for example, annual extreme precipitation).
Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.
Please make sure to update tests as appropriate.
Copyright © 2021 Nick Rong
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