How to fit distribution models for a frequency analysis?

In summary, the conversation discusses using rainfall data from a catch basin to determine the fittest distribution model for frequency analysis. This involves fitting log-Pearson Type III and Gumbel distributions to the plot and measuring the fit using Chi-square goodness of fit. The goal is to obtain "predicted" rainfall depths using the chosen distribution model to perform the fitting test and determine the most appropriate distribution for modeling the rainfall frequency. However, there is uncertainty on how to obtain the "predicted" rainfall depth needed for the chi-square goodness of fit test.
  • #1
median27
58
0
I have a rainfall (mm) vs. year plot of a catch basin (see Excel file below) and I would like to get it's frequency curve. But before that, I need to fit certain distribution models (i.e. log-Pearson Type III and Gumbel Distributions) to my plot to be able to know the fittest model that I can use for my frequency analysis. How will I do that?

(I'll measure the fit using Chi-square goodness of fit.)
 

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  • rainfall.xlsx
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  • #2
It's not clear what you mean by 'frequency curve'. Your data appear to be cumulative rainfall amounts sampled on an annual basis.
 
  • #3
The plotted data are the "observed" data for the annual maximum rainfall - daily basis. I need to get the "predicted" rainfall depths using the said distributions above and perform the fitting test. The fittest distribution will be the appropriate distribution to model the rainfall frequency of the catch basin. My only problem is, I don't know how to get the "predicted" rainfall depth which is needed in performing the chi-square goodness of fit test.
 

1. What is a frequency analysis?

A frequency analysis is a statistical technique used to model the distribution of a set of data based on the frequency of its values. It helps to identify the most common values and patterns in the data, which can then be used to make predictions or draw conclusions.

2. Why is fitting distribution models important in frequency analysis?

Fitting distribution models is important in frequency analysis because it helps to determine the best mathematical function that describes the data distribution. This allows for better understanding and interpretation of the data, as well as more accurate predictions and inferences.

3. What are some common distribution models used in frequency analysis?

Some common distribution models used in frequency analysis include the normal distribution, log-normal distribution, exponential distribution, and Weibull distribution. These models have different shapes and characteristics, and are chosen based on the type of data being analyzed.

4. How do you fit a distribution model for a frequency analysis?

To fit a distribution model for a frequency analysis, you first need to plot a histogram of the data to visually inspect its shape and distribution. Then, you can use statistical software or programming languages to fit different distribution models and compare their goodness of fit using measures such as the chi-square test or Kolmogorov-Smirnov test.

5. What are some challenges in fitting distribution models for a frequency analysis?

One of the main challenges in fitting distribution models for a frequency analysis is choosing the most appropriate model for the data. This can be difficult as there are many different distribution models to choose from, and the data may not always fit perfectly into one specific model. Additionally, the accuracy of the fit may be affected by the size and quality of the data, as well as the assumptions made about the data distribution.

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