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Student distribution value

Student distribution value

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This function retrieve the student distribution value for a given alpha and degree of freedom value.

studentvalue(a,n)
function [st,alpha,perc] = studentvalue(a,n)
%% This function retrieve the student
% distribution value for a given alpha and
% degree of freedom value.
%
% File created on Mar 5th 2008
%
% Last modified: Jan 29th 2009
%
% Author: Arnaud Laurent
%
%   Inputs: a = can be any alpha value
%           n = number of data points
%
%   Output: st = value of the student distribution
%           alpha = the alpha value used
%           perc = the corresponding percentage
%
%	Comment: a can be expressed in percent
%
df = n-2; % Degree of freedom

ttable = ini_ttable;

row = cls(ttable(:,1),df)
row=row(1);

if a>1
    col = cls(ttable(end,:),a);
else
    col = cls(ttable(1,:),a);
end
col=col(2);

st = ttable(row,col);
alpha = ttable(1,col);
perc = ttable(end,col);

%%%%%
function idx = cls(x,a)
%% This function retrieve the column and row
% of the closest value to a in x

[idx(1),idx(2)] = find(abs(x-a)==nanmin(nanmin(abs(x-a))));

%%%%%
function x = ini_ttable
%% This function creates the t-table
%
x = [nan,0.25,0.15,0.1,0.05,0.025,0.01,0.005,0.001,0.0005;
1,1.376,1.963,3.078,6.314,12.706,31.821,63.657,318.310,636.620;
2,1.061,1.386,1.886,2.920,4.303,6.965,9.925,22.327,31.599;
3,0.978,1.250,1.638,2.353,3.182,4.541,5.841,10.215,12.924;
4,0.941,1.190,1.533,2.132,2.776,3.747,4.604,7.173,8.610;
5,0.920,1.156,1.476,2.015,2.571,3.365,4.032,5.893,6.869;
6,0.906,1.134,1.440,1.943,2.447,3.143,3.707,5.208,5.959;
7,0.896,1.119,1.415,1.895,2.365,2.998,3.499,4.785,5.408;
8,0.889,1.108,1.397,1.860,2.306,2.896,3.355,4.501,5.041;
9,0.883,1.100,1.383,1.833,2.262,2.821,3.250,4.297,4.781;
10,0.879,1.093,1.372,1.812,2.228,2.764,3.169,4.144,4.587;
11,0.876,1.088,1.363,1.796,2.201,2.718,3.106,4.025,4.437;
12,0.873,1.083,1.356,1.782,2.179,2.681,3.055,3.930,4.318;
13,0.870,1.079,1.350,1.771,2.160,2.650,3.012,3.852,4.221;
14,0.868,1.076,1.345,1.761,2.145,2.624,2.977,3.787,4.140;
15,0.866,1.074,1.341,1.753,2.131,2.602,2.947,3.733,4.073;
16,0.865,1.071,1.337,1.746,2.120,2.583,2.921,3.686,4.015;
17,0.863,1.069,1.333,1.740,2.110,2.567,2.898,3.646,3.965;
18,0.862,1.067,1.330,1.734,2.101,2.552,2.878,3.610,3.922;
19,0.861,1.066,1.328,1.729,2.093,2.539,2.861,3.579,3.883;
20,0.860,1.064,1.325,1.725,2.086,2.528,2.845,3.552,3.850;
21,0.859,1.063,1.323,1.721,2.080,2.518,2.831,3.527,3.819;
22,0.858,1.061,1.321,1.717,2.074,2.508,2.819,3.505,3.792;
23,0.858,1.060,1.319,1.714,2.069,2.500,2.807,3.485,3.768;
24,0.857,1.059,1.318,1.711,2.064,2.492,2.797,3.467,3.745;
25,0.856,1.058,1.316,1.708,2.060,2.485,2.787,3.450,3.725;
26,0.856,1.058,1.315,1.706,2.056,2.479,2.779,3.435,3.707;
27,0.855,1.057,1.314,1.703,2.052,2.473,2.771,3.421,3.690;
28,0.855,1.056,1.313,1.701,2.048,2.467,2.763,3.408,3.674;
29,0.854,1.055,1.311,1.699,2.045,2.462,2.756,3.396,3.659;
30,0.854,1.055,1.310,1.697,2.042,2.457,2.750,3.385,3.646;
40,0.851,1.050,1.303,1.684,2.021,2.423,2.704,3.307,3.551;
50,0.849,1.047,1.299,1.676,2.009,2.403,2.678,3.261,3.496;
75,0.846,1.044,1.293,1.665,1.992,2.377,2.643,3.202,3.425;
100,0.845,1.042,1.290,1.660,1.984,2.364,2.626,3.174,3.390;
200,0.843,1.039,1.286,1.653,1.972,2.345,2.601,3.131,3.340;
1000,0.842,1.037,1.282,1.646,1.962,2.330,2.581,3.098,3.300;
2000,0.841,1.036,1.282,1.645,1.960,2.326,2.576,3.091,3.291;
nan	50,70,80,90,95,98,99,99.8,99.9];

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