1 | FUNCTION stat_error, data, window, DATA2 = data2, NITER = niter, BAVARD = bavard, MEAN = mean |
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2 | |
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3 | ; ------------------------------------ |
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4 | ; Program to estimate statistical error of either one time series (std) |
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5 | ; or significance of std dev difference between two time series |
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6 | |
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7 | ; (c) 2005, E. Guilyardi - thanks to Pascal Terray for theory |
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8 | |
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9 | ; Errors are estimated using a moving block bootstrap (of length |
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10 | ; 'window') to account for serial correlations |
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11 | |
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12 | ; INPUTS |
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13 | ; data: 1d array |
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14 | ; window: window size (int) |
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15 | ; NITER = number of iteration (999 by default to have 1% precision) |
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16 | |
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17 | ; 0. Inits |
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18 | ; --------- |
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19 | |
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20 | niter1 = 999 |
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21 | IF keyword_set(niter) THEN niter1 = niter |
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22 | |
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23 | errstats = fltarr(niter1) |
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24 | |
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25 | ; define array: either [data] or [data, data2] |
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26 | |
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27 | |
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28 | IF keyword_set(data2) THEN BEGIN |
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29 | ; 2 arrays |
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30 | array = [data, data2] |
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31 | nblocks = floor(n_elements(data2)/window) |
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32 | IF n_elements(data2) NE nblocks*window THEN BEGIN |
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33 | print, ' ERROR: window must divide data2 size: ', n_elements(data2), window |
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34 | return, -1 |
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35 | ENDIF |
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36 | sizetest = n_elements(data2) |
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37 | ENDIF ELSE BEGIN |
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38 | ; 1 array |
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39 | array = data |
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40 | nblocks = floor(n_elements(data)/window) |
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41 | ; IF n_elements(data) NE nblocks*window THEN BEGIN |
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42 | ; print, ' ERROR: window must divide data size: ', n_elements(data), window |
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43 | ; return, -1 |
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44 | ; ENDIF |
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45 | sizetest = n_elements(data) |
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46 | ENDELSE |
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47 | |
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48 | size = n_elements(array) |
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49 | nblockst = floor(size/window) |
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50 | |
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51 | IF keyword_set(bavard) THEN BEGIN |
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52 | |
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53 | print, ' Error stats on array size/min/max: ', size, min(array), max(array) |
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54 | print, ' using moving window of ', window, ' with N iter =', niter1 |
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55 | print, ' total number of blocks', nblockst |
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56 | print, ' number of blocks and size of test array', nblocks, sizetest |
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57 | |
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58 | ENDIF |
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59 | |
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60 | it = 0 |
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61 | seed = 0 |
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62 | |
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63 | idx0 = findgen(window) |
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64 | |
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65 | |
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66 | WHILE it LE niter1-1 DO BEGIN |
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67 | ; |
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68 | ; 1. Randomly define blocks |
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69 | ; ------------------------- |
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70 | ib = 0 |
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71 | rand = fix(nblockst*randomu(seed, nblocks)) |
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72 | |
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73 | testarr = array[(rand(0)*window)+idx0] |
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74 | |
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75 | WHILE ib LE nblocks - 2 DO BEGIN |
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76 | |
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77 | testarr = [testarr, array((rand(ib)*window)+idx0)] |
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78 | ib = ib + 1 |
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79 | ENDWHILE |
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80 | ; |
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81 | ; 2. Compute stats |
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82 | ; ---------------- |
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83 | IF keyword_set(mean) THEN BEGIN |
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84 | errstats(it) = mean(testarr) |
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85 | ENDIF ELSE BEGIN |
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86 | ; errstats(it) = sqrt((moment(testarr))[1]) |
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87 | errstats(it) = sqrt( total(testarr^2)/n_elements(testarr)) |
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88 | ENDELSE |
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89 | ; method 1 keep mean i.e = sqrt(sum(testarr(i)**2)/N) |
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90 | ; method 2 errstats(it) = sqrt((moment(testarr))[1]) |
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91 | |
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92 | it = it + 1 |
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93 | ENDWHILE |
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94 | |
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95 | ; |
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96 | ; 3. Organise output |
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97 | ; ------------------ |
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98 | ; |
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99 | |
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100 | return, errstats |
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101 | |
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102 | END |
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