author | A.M. Thurnherr <athurnherr@yahoo.com> |
Tue, 29 Jun 2021 09:14:43 -0400 | |
changeset 23 | e83393696a24 |
parent 0 | 0a450563f904 |
permissions | -rw-r--r-- |
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%====================================================================== |
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% B E S T T L A G . M |
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% doc: Wed Jul 19 15:34:53 2006 |
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% dlm: Fri Mar 5 15:50:57 2010 |
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% (c) 2006 M. Visbeck |
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% uE-Info: 51 16 NIL 0 0 72 0 2 4 NIL ofnI |
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%====================================================================== |
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|
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function [lag,co]=besttlag(a1,a2,nlag,npoint,nsect) |
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% function [lag,co]=besttlag(a1,a2,nlag,npoint,nsect) |
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% |
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12 |
% function to find the best shift for two vectors |
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% uses median difference |
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% |
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15 |
% input: a1: first vector (time,variable) should be the high resolution one |
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% a2: second vector(time,variable) |
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% nlag = number of point to try shifiting |
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% npoint = use how many points |
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% nsect = number of chunks of data to use |
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% |
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% M. Visbeck LDEO August-2002 |
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|
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% MODIFICATIONS BY ANT: |
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% Jul 19, 2006: - removed NaNs before interp1() to avoid Matlab 7.2 warning |
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|
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l1=size(a1,1); |
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l2=size(a2,1); |
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|
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if nargin<4, npoint=min(length(a1),3*nlag); end |
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if nargin<5, nsect=ceil(l1/(npoint)); end |
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if nargin<3, nlag=fix(npoint/8); end |
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|
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% loop over chunks of data to be used avoid begining and end |
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ismed=round(linspace(1,l1,nsect+4)); |
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ismed([1,2, end-1, end])=[]; |
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|
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% add largest gradient to list |
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iok=fix(l1*0.25):(l1*.75); |
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[dum,ii]=find(maxnan(abs(diff(a1(iok,2))))); |
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ismed(end+1)=iok(ii); |
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|
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for i=1:length(ismed) |
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|
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% select data for section |
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isect=[-fix(npoint/2):(npoint/2)]+ismed(i); |
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iok=find(isect>0 & isect<l1); |
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isect=isect(iok); |
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|
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% interpolate a2 on a1 with regards to time |
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igood = find(isfinite(a2(:,2))); |
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a22=interp1(a2(igood,1),a2(igood,2),a1(isect,1),'nearest'); |
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a12=a1(isect,2); |
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[lagv(i),i1,i2,cov(i)]=bestlag(a12,a22,nlag); |
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if lagv(i)==0 & cov(i)==1, cov(i)=nan; end |
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disp([' lag: ',int2str(lagv(i)),' correlation: ',num2str(cov(i))]) |
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|
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end |
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|
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if maxnan(cov)<0.97 |
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% try acceleration near large w-difference |
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i=length(lagv)+1; |
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[lagv(i),i1,i2,cov(i)]=bestlag(diff(a12),diff(a22),nlag); |
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disp([' acceleration lag: ',int2str(lagv(i)),' correlation: ',num2str(cov(i))]) |
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end |
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|
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if maxnan(cov)<0.97 |
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% one scan over whole length of max correlation was not great |
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i=length(lagv)+1; |
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isect=nlag:(length(a1)-nlag); |
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a22=interp1(a2(:,1),a2(:,2),a1(isect,1),'nearest'); |
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a12=a1(isect,2); |
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[lagv(i),i1,i2,cov(i)]=bestlag(a12,a22,nlag); |
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disp([' all data lag: ',int2str(lagv(i)),' correlation: ',num2str(cov(i))]) |
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end |
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|
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if maxnan(cov)<0.97 |
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% one scan over whole length of max correlation was not great |
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i=length(lagv)+1; |
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ii=find(~isfinite(a12)); a12(ii)=0; |
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ii=find(~isfinite(a22)); a22(ii)=0; |
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[lagv(i),i1,i2,cov(i)]=bestlag(cumsum(a12),cumsum(a22),nlag); |
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disp([' all data integral lag: ',int2str(lagv(i)),' correlation: ',num2str(cov(i))]) |
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84 |
end |
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85 |
|
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86 |
% choose the most likely lag |
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ii=find(~isfinite(cov)); |
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cov(ii)=[]; |
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lagv(ii)=[]; |
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if length(lagv)>2 |
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lag0=median(lagv); |
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92 |
else |
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lag0=nan; |
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94 |
end |
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95 |
disp([' median lag ',int2str(lag0)]) |
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96 |
nnlag=-nlag:nlag; |
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lagh=hist(lagv,nnlag); |
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98 |
% prefer 0 lag slightly |
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[nlag1,i1]=max(lagh-abs(nnlag)/(2*max(nnlag))); |
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lag1=nnlag(i1); |
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101 |
iok=find(lag1==lagv); |
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102 |
co=meannan(cov(iok)); |
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103 |
disp([' most popular lag ',int2str(lag1)]) |
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104 |
[cos,is]=sort(cov); |
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105 |
lags=lagv(is); |
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106 |
lag2=lags(end); |
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107 |
disp([' best correlated lag ',int2str(lag2)]) |
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108 |
% decide which one to use |
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109 |
if co*sqrt(length(iok)) > cos(end) |
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110 |
lag=lag1; |
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111 |
else |
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112 |
lag=lag2; |
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113 |
end |
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114 |
iok=find(lag==lagv); |
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115 |
co=maxnan(cov(iok)); |
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116 |
|
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117 |
disp([' BESTTLAG: lag is: ',int2str(lag),' for which ',... |
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118 |
int2str(length(iok)/nsect*100),'% of ',int2str(nsect),' lags agree']) |
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119 |
|
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120 |
return |
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121 |
|
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122 |
%=============================== |
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123 |
function y = median(x,dim) |
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124 |
%MEDIAN Median value. |
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125 |
% For vectors, MEDIAN(X) is the median value of the elements in X. |
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126 |
% For matrices, MEDIAN(X) is a row vector containing the median |
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127 |
% value of each column. For N-D arrays, MEDIAN(X) is the median |
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128 |
% value of the elements along the first non-singleton dimension |
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129 |
% of X. |
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130 |
% |
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131 |
% MEDIAN(X,DIM) takes the median along the dimension DIM of X. |
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132 |
% |
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133 |
% Example: If X = [0 1 2 |
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134 |
% 3 4 5] |
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135 |
% |
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136 |
% then median(X,1) is [1.5 2.5 3.5] and median(X,2) is [1 |
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137 |
% 4] |
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138 |
% |
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139 |
% See also MEAN, STD, MIN, MAX, COV. |
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140 |
|
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141 |
% Copyright 1984-2002 The MathWorks, Inc. |
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142 |
% $Revision: 5.15 $ $Date: 2002/06/05 17:06:39 $ |
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143 |
|
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144 |
if nargin==1, |
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145 |
dim = min(find(size(x)~=1)); |
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146 |
if isempty(dim), dim = 1; end |
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147 |
end |
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148 |
if isempty(x), y = []; return, end |
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149 |
|
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150 |
siz = [size(x) ones(1,dim-ndims(x))]; |
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151 |
n = size(x,dim); |
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152 |
|
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153 |
% Permute and reshape so that DIM becomes the row dimension of a 2-D array |
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154 |
perm = [dim:max(length(size(x)),dim) 1:dim-1]; |
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155 |
x = reshape(permute(x,perm),n,prod(siz)/n); |
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156 |
|
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157 |
% Sort along first dimension |
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158 |
x = sort(x,1); |
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159 |
|
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160 |
if rem(n,2) % Odd number of elements along DIM |
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161 |
y = x((n+1)/2,:); |
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162 |
else % Even number of elements along DIM |
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163 |
% y = (x(n/2,:) + x((n/2)+1,:))/2; |
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164 |
y = x(fix((n/2)+1),:); |
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165 |
end |
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166 |
|
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167 |
% Check for NaNs |
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168 |
y(isnan(x(1,:)) | isnan(x(n,:))) = NaN; |
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169 |
|
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170 |
% Permute and reshape back |
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171 |
siz(dim) = 1; |
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172 |
y = ipermute(reshape(y,siz(perm)),perm); |