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# wgumbplot

## PURPOSE

Plots data on a Gumbel distribution paper.

## SYNOPSIS

phat = wgumbplot(x)

## DESCRIPTION

``` WGUMBPLOT Plots data on a Gumbel distribution paper.

CALL:  phat = wgumbplot(X)

phat = [a b] Parameters (see wgumbcdf) estimated from the plot by
least squares method
X = data vector or matrix

Example:
R=wgumbrnd(2,0,[],1,100);
phat=wgumbplot(R)```

## CROSS-REFERENCE INFORMATION

This function calls:
 empdistr Computes and plots the empirical CDF hold Hold current graph. plot Linear plot. title Graph title. xlabel X-axis label. ylabel Y-axis label.
This function is called by:
 Chapter5 % CHAPTER5 contains the commands used in Chapter 5 of the tutorial dist2dfit Parameter estimates for DIST2D data.

## SOURCE CODE

```001 function phat = wgumbplot(x)
002 %WGUMBPLOT Plots data on a Gumbel distribution paper.
003 %
004 % CALL:  phat = wgumbplot(X)
005 %
006 %       phat = [a b] Parameters (see wgumbcdf) estimated from the plot by
007 %              least squares method
008 %          X = data vector or matrix
009 %
010 % Example:
011 %   R=wgumbrnd(2,0,[],1,100);
012 %   phat=wgumbplot(R)
013
014 % Reference:
015 %  Johnson  N.L., Kotz S. and Balakrishnan, N. (1994)
016 %  Continuous Univariate Distributions, Volume 2. Wiley.
017
018
019 % rewritten ms 20.06.2000
020
021 F=empdistr(x,[],0);
022 plot(F(:,1),-log(-log(F(:,2))),'b.','markersize',12);
023 U=[ones(size(F(:,1))) F(:,1)];
024 c=U\(-log(-log(F(:,2))));
025 a=1/c(2);
026 b=-c(1)*a;
027 hold on
028 plot(F(:,1),U*c,'r--')
029 hold off
030 title('Gumbel Probability Plot')
031 xlabel('X')
032 ylabel('-log(-log(F))')
033 if nargout > 0,
034   phat=[a,b];
035 end
036```

Mathematical Statistics
Centre for Mathematical Sciences
Lund University with Lund Institute of Technology

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