Statistics: burrfit

### Function Reference: `burrfit`

statistics: paramhat = burrfit (x)
statistics: [paramhat, paramci] = burrfit (x)
statistics: [paramhat, paramci] = burrfit (x, alpha)
statistics: […] = burrfit (x, alpha, censor)
statistics: […] = burrfit (x, alpha, censor, freq)
statistics: […] = burrfit (x, alpha, censor, freq, options)

Estimate mean and confidence intervals for the Burr type XII distribution.

`muhat = burrfit (x)` returns the maximum likelihood estimates of the parameters of the Burr type XII distribution given the data in x. `paramhat(1)` is the scale parameter, lambda, `paramhat(2)` is the first shape parameter, c, and `paramhat(3)` is the second shape parameter, k

`[paramhat, paramci] = burrfit (x)` returns the 95% confidence intervals for the parameter estimates.

`[…] = burrfit (x, alpha)` also returns the `100 * (1 - alpha)` percent confidence intervals for the parameter estimates. By default, the optional argument alpha is 0.05 corresponding to 95% confidence intervals. Pass in `[]` for alpha to use the default values.

`[…] = burrfit (x, alpha, censor)` accepts a boolean vector, censor, of the same size as x with `1`s for observations that are right-censored and `0`s for observations that are observed exactly. By default, or if left empty, `censor = zeros (size (x))`.

`[…] = burrfit (x, alpha, censor, freq)` accepts a frequency vector, freq, of the same size as x. freq typically contains integer frequencies for the corresponding elements in x, but it can contain any non-integer non-negative values. By default, or if left empty, `freq = ones (size (x))`.

`[…] = burrfit (…, options)` specifies control parameters for the iterative algorithm used to compute ML estimates with the `fminsearch` function. options is a structure with the following fields and their default values:

- `options.Display = "off"`
- `options.MaxFunEvals = 1000`
- `options.MaxIter = 500`
- `options.TolX = 1e-6`

Further information about the Burr type XII distribution can be found at https://en.wikipedia.org/wiki/Burr_distribution

See also: burrcdf, burrinv, burrpdf, burrrnd, burrlike, burrstat

Source Code: burrfit

### Example: 1

     ## Sample 3 populations from different Burr type XII distibutions
     rand ("seed", 4);    # for reproducibility
     r1 = burrrnd (3.5, 2, 2.5, 10000, 1);
     rand ("seed", 2);    # for reproducibility
     r2 = burrrnd (1, 3, 1, 10000, 1);
     rand ("seed", 9);    # for reproducibility
     r3 = burrrnd (0.5, 2, 3, 10000, 1);
     r = [r1, r2, r3];

     ## Plot them normalized and fix their colors
     hist (r, [0.1:0.2:20], [18, 5, 3]);
     h = findobj (gca, "Type", "patch");
     set (h(1), "facecolor", "c");
     set (h(2), "facecolor", "g");
     set (h(3), "facecolor", "r");
     ylim ([0, 3]);
     xlim ([0, 5]);
     hold on

     ## Estimate their α and β parameters
     lambda_c_kA = burrfit (r(:,1));
     lambda_c_kB = burrfit (r(:,2));
     lambda_c_kC = burrfit (r(:,3));

     ## Plot their estimated PDFs
     x = [0.01:0.15:15];
     y = burrpdf (x, lambda_c_kA(1), lambda_c_kA(2), lambda_c_kA(3));
     plot (x, y, "-pr");
     y = burrpdf (x, lambda_c_kB(1), lambda_c_kB(2), lambda_c_kB(3));
     plot (x, y, "-sg");
     y = burrpdf (x, lambda_c_kC(1), lambda_c_kC(2), lambda_c_kC(3));
     plot (x, y, "-^c");
     hold off
     legend ({"Normalized HIST of sample 1 with λ=3.5, c=2, and k=2.5", ...
              "Normalized HIST of sample 2 with λ=1, c=3, and k=1", ...
              "Normalized HIST of sample 3 with λ=0.5, c=2, and k=3", ...
      sprintf("PDF for sample 1 with estimated λ=%0.2f, c=%0.2f, and k=%0.2f", ...
              lambda_c_kA(1), lambda_c_kA(2), lambda_c_kA(3)), ...
      sprintf("PDF for sample 2 with estimated λ=%0.2f, c=%0.2f, and k=%0.2f", ...
              lambda_c_kB(1), lambda_c_kB(2), lambda_c_kB(3)), ...
      sprintf("PDF for sample 3 with estimated λ=%0.2f, c=%0.2f, and k=%0.2f", ...
              lambda_c_kC(1), lambda_c_kC(2), lambda_c_kC(3))})
     title ("Three population samples from different Burr type XII distibutions")
     hold off