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<html xmlns:mwsh="http://www.mathworks.com/namespace/mcode/v1/syntaxhighlight.dtd"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <!--This HTML is auto-generated from an M-file.To make changes, update the M-file and republish this document. --> <title>Example</title> <meta name="generator" content="MATLAB 7.0"> <meta name="date" content="2004-10-18"> <meta name="m-file" content="wtcdemo"><style>body { background-color: white; margin:10px;}h1 { color: #990000; font-size: x-large;}h2 { color: #990000; font-size: medium;}p.footer { text-align: right; font-size: xx-small; font-weight: lighter; font-style: italic; color: gray;}pre.codeinput { margin-left: 30px;}span.keyword {color: #0000FF}span.comment {color: #228B22}span.string {color: #A020F0}span.untermstring {color: #B20000}span.syscmd {color: #B28C00}pre.showbuttons { margin-left: 30px; border: solid black 2px; padding: 4px; background: #EBEFF3;}pre.codeoutput { color: gray; font-style: italic;}pre.error { color: red;}/* Make the text shrink to fit narrow windows, but not stretch too far in wide windows. On Gecko-based browsers, the shrink-to-fit doesn't work. */ p,h1,h2,div { /* for MATLAB's browser */ width: 600px; /* for Mozilla, but the "width" tag overrides it anyway */ max-width: 600px; /* for IE */ width:expression(document.body.clientWidth > 620 ? "600px": "auto" );} </style></head> <body> <h1>Example</h1> <introduction> <p>This example illustrates how simple it is to do continuous wavelet transform (CWT), Cross wavelet transform (XWT) and Wavelet Coherence (WTC) plots of your own data. </p> <p>The time series we will be analyzing are the winter Arctic Oscillation index (AO) and the maximum sea ice extent in the Baltic (BMI). </p> <p><a href="http://www.pol.ac.uk/home/research/waveletcoherence/">http://www.pol.ac.uk/home/research/waveletcoherence/</a></p> </introduction> <h2>Contents</h2> <div> <ul> <li><a href="#1">Load the data</a></li> <li><a href="#2">Change the pdf.</a></li> <li><a href="#3">Continuous wavelet transform (CWT)</a></li> <li><a href="#4">Cross wavelet transform (XWT)</a></li> <li><a href="#5">Wavelet coherence (WTC)</a></li> <li><a href="#6">Copyright notice</a></li> </ul> </div> <h2>Load the data<a name="1"></a></h2> <p>First we load the two time series into the matrices d1 and d2.</p><pre class="codeinput">seriesname={<span class="string">'AO'</span> <span class="string">'BMI'</span>};d1=load(<span class="string">'jao.txt'</span>);d2=load(<span class="string">'jbaltic.txt'</span>);</pre><h2>Change the pdf.<a name="2"></a></h2> <p>The time series of Baltic Sea ice extent is highly bi-modal and we therefore transform the timeseries into a series of percentiles. The transformed series probably reacts 'more linearly' to climate. </p><pre class="codeinput">d2(:,2)=boxpdf(d2(:,2));</pre><h2>Continuous wavelet transform (CWT)<a name="3"></a></h2> <p>The CWT expands the time series into time frequency space.</p><pre class="codeinput">figure(<span class="string">'color'</span>,[1 1 1])tlim=[min(d1(1,1),d2(1,1)) max(d1(end,1),d2(end,1))];subplot(2,1,1);wt(d1);title(seriesname{1});set(gca,<span class="string">'xlim'</span>,tlim);subplot(2,1,2)wt(d2)title(seriesname{2})set(gca,<span class="string">'xlim'</span>,tlim)</pre><img vspace="5" hspace="5" src="wtcdemo_01.png"> <h2>Cross wavelet transform (XWT)<a name="4"></a></h2> <p>The XWT finds regions in time frequency space where the time series show high common power.</p><pre class="codeinput">figure(<span class="string">'color'</span>,[1 1 1])xwt(d1,d2)title([<span class="string">'XWT: '</span> seriesname{1} <span class="string">'-'</span> seriesname{2} ] )</pre><img vspace="5" hspace="5" src="wtcdemo_02.png"> <h2>Wavelet coherence (WTC)<a name="5"></a></h2> <p>The WTC finds regions in time frequency space where the two time series co-vary (but does not necessarily have high power).</p><pre class="codeinput">figure(<span class="string">'color'</span>,[1 1 1])wtc(d1,d2)title([<span class="string">'WTC: '</span> seriesname{1} <span class="string">'-'</span> seriesname{2} ] )</pre><img vspace="5" hspace="5" src="wtcdemo_03.png"> <h2>Copyright notice<a name="6"></a></h2><pre> Copyright (C) 2002-2004, Aslak Grinsted</pre><pre> This software may be used, copied, or redistributed as long as it is not sold and this copyright notice is reproduced on each copy made. This routine is provided as is without any express or implied warranties whatsoever.</pre><p class="footer"><br> Published with MATLAB® 7.0<br></p> <!--##### SOURCE BEGIN #####%% Example
% This example illustrates how simple it is to do
% continuous wavelet transform (CWT), Cross wavelet transform (XWT)
% and Wavelet Coherence (WTC) plots of your own data.
%
% The time series we will be analyzing are the winter
% Arctic Oscillation index (AO) and
% the maximum sea ice extent in the Baltic (BMI).
%
% http://www.pol.ac.uk/home/research/waveletcoherence/
%% Load the data
% First we load the two time series into the matrices d1 and d2.
seriesname={'AO' 'BMI'};
d1=load('jao.txt');
d2=load('jbaltic.txt');
%% Change the pdf.
% The time series of Baltic Sea ice extent is highly bi-modal and we
% therefore transform the timeseries into a series of percentiles. The
% transformed series probably reacts 'more linearly' to climate.
d2(:,2)=boxpdf(d2(:,2));
%% Continuous wavelet transform (CWT)
% The CWT expands the time series into time
% frequency space.
figure('color',[1 1 1])
tlim=[min(d1(1,1),d2(1,1)) max(d1(end,1),d2(end,1))];
subplot(2,1,1);
wt(d1);
title(seriesname{1});
set(gca,'xlim',tlim);
subplot(2,1,2)
wt(d2)
title(seriesname{2})
set(gca,'xlim',tlim)
%% Cross wavelet transform (XWT)
% The XWT finds regions in time frequency space where
% the time series show high common power.
figure('color',[1 1 1])
xwt(d1,d2)
title(['XWT: ' seriesname{1} '-' seriesname{2} ] )
%% Wavelet coherence (WTC)
% The WTC finds regions in time frequency space where the two
% time series co-vary (but does not necessarily have high power).
figure('color',[1 1 1])
wtc(d1,d2)
title(['WTC: ' seriesname{1} '-' seriesname{2} ] )
%% Copyright notice
% Copyright (C) 2002-2004, Aslak Grinsted
%
% This software may be used, copied, or redistributed as long as it is not
% sold and this copyright notice is reproduced on each copy made. This
% routine is provided as is without any express or implied warranties
% whatsoever.##### SOURCE END #####--> </body></html>⌨️ 快捷键说明
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