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<div><a href="../index.html">Home</a> &gt; <a href="index.html">.</a> &gt; UnivariateSpectralDensity.m</div>
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<h1>UnivariateSpectralDensity
</h1>
<h2><a name="_name"></a>PURPOSE <a href="#_top"><img alt="^" border="0" src="../up.png"></a></h2>
<div class="box"><strong>stephane.adjemian@ens.fr</strong></div>
<h2><a name="_synopsis"></a>SYNOPSIS <a href="#_top"><img alt="^" border="0" src="../up.png"></a></h2>
<div class="box"><strong>function [omega,f] = UnivariateSpectralDensity(dr,var_list) </strong></div>
<h2><a name="_description"></a>DESCRIPTION <a href="#_top"><img alt="^" border="0" src="../up.png"></a></h2>
<div class="fragment"><pre class="comment"> stephane.adjemian@ens.fr
This function computes the theoretical spectral density of each
endogenous variable declared in var_list. Results are stored in
oo_ and may be plotted.
Adapted from th_autocovariances.m.</pre></div>
<!-- crossreference -->
<h2><a name="_cross"></a>CROSS-REFERENCE INFORMATION <a href="#_top"><img alt="^" border="0" src="../up.png"></a></h2>
This function calls:
<ul style="list-style-image:url(../matlabicon.gif)">
<li><a href="kalman_transition_matrix.html" class="code" title="function [A,B] = kalman_transition_matrix(dr)">kalman_transition_matrix</a> makes transition matrices out of ghx and ghu for Kalman filter</li><li><a href="lyapunov_symm.html" class="code" title="function [x,ns_var]=lyapunov_symm(a,b)">lyapunov_symm</a> solves x-a*x*a'=b for b (and then x) symmetrical</li></ul>
This function is called by:
<ul style="list-style-image:url(../matlabicon.gif)">
<li><a href="stoch_simul.html" class="code" title="function info=stoch_simul(var_list)">stoch_simul</a> Copyright (C) 2001 Michel Juillard</li></ul>
<!-- crossreference -->
<h2><a name="_source"></a>SOURCE CODE <a href="#_top"><img alt="^" border="0" src="../up.png"></a></h2>
<div class="fragment"><pre>0001 <span class="comment">% stephane.adjemian@ens.fr</span>
0002 <a name="_sub0" href="#_subfunctions" class="code">function [omega,f] = UnivariateSpectralDensity(dr,var_list)</a>
0003 <span class="comment">% This function computes the theoretical spectral density of each</span>
0004 <span class="comment">% endogenous variable declared in var_list. Results are stored in</span>
0005 <span class="comment">% oo_ and may be plotted.</span>
0006 <span class="comment">%</span>
0007 <span class="comment">% Adapted from th_autocovariances.m.</span>
0008 <span class="keyword">global</span> options_ oo_ M_
0009
0010 omega = []; f = [];
0011
0012 <span class="keyword">if</span> options_.order &gt; 1
0013 disp(<span class="string">'UnivariateSpectralDensity :: I Cannot compute the theoretical spectral density'</span>)
0014 disp(<span class="string">'with a second order approximation of the DSGE model!'</span>)
0015 disp(<span class="string">'Set order = 1.'</span>)
0016 <span class="keyword">return</span>
0017 <span class="keyword">end</span>
0018
0019 pltinfo = 1;<span class="comment">%options_.SpectralDensity.Th.plot;</span>
0020 cutoff = 100;<span class="comment">%options_.SpectralDensity.Th.cutoff;</span>
0021 sdl = 0.1;<span class="comment">%options_.SepctralDensity.Th.sdl;</span>
0022 omega = (0:sdl:pi)';
0023 GridSize = length(omega);
0024 exo_names_orig_ord = M_.exo_names_orig_ord;
0025 <span class="keyword">if</span> sscanf(version(<span class="string">'-release'</span>),<span class="string">'%d'</span>) &lt; 13
0026 warning off
0027 <span class="keyword">else</span>
0028 eval(<span class="string">'warning off MATLAB:dividebyzero'</span>)
0029 <span class="keyword">end</span>
0030 <span class="keyword">if</span> nargin&lt;2
0031 var_list = [];
0032 <span class="keyword">end</span>
0033 nvar = size(var_list,1);
0034 <span class="keyword">if</span> nvar == 0
0035 nvar = length(dr.order_var);
0036 ivar = [1:nvar]';
0037 <span class="keyword">else</span>
0038 ivar=zeros(nvar,1);
0039 <span class="keyword">for</span> i=1:nvar
0040 i_tmp = strmatch(var_list(i,:),M_.endo_names,<span class="string">'exact'</span>);
0041 <span class="keyword">if</span> isempty(i_tmp)
0042 error ([<span class="string">'One of the variable specified does not exist'</span>]) ;
0043 <span class="keyword">else</span>
0044 ivar(i) = i_tmp;
0045 <span class="keyword">end</span>
0046 <span class="keyword">end</span>
0047 <span class="keyword">end</span>
0048 f = zeros(nvar,GridSize);
0049 ghx = dr.ghx;
0050 ghu = dr.ghu;
0051 npred = dr.npred;
0052 nstatic = dr.nstatic;
0053 kstate = dr.kstate;
0054 order = dr.order_var;
0055 iv(order) = [1:length(order)];
0056 nx = size(ghx,2);
0057 ikx = [nstatic+1:nstatic+npred];
0058 A = zeros(nx,nx);
0059 k0 = kstate(find(kstate(:,2) &lt;= M_.maximum_lag+1),:);
0060 i0 = find(k0(:,2) == M_.maximum_lag+1);
0061 i00 = i0;
0062 n0 = length(i0);
0063 A(i0,:) = ghx(ikx,:);
0064 AS = ghx(:,i0);
0065 ghu1 = zeros(nx,M_.exo_nbr);
0066 ghu1(i0,:) = ghu(ikx,:);
0067 <span class="keyword">for</span> i=M_.maximum_lag:-1:2
0068 i1 = find(k0(:,2) == i);
0069 n1 = size(i1,1);
0070 j1 = zeros(n1,1);
0071 j2 = j1;
0072 <span class="keyword">for</span> k1 = 1:n1
0073 j1(k1) = find(k0(i00,1)==k0(i1(k1),1));
0074 j2(k1) = find(k0(i0,1)==k0(i1(k1),1));
0075 <span class="keyword">end</span>
0076 AS(:,j1) = AS(:,j1)+ghx(:,i1);
0077 i0 = i1;
0078 <span class="keyword">end</span>
0079 b = ghu1*M_.Sigma_e*ghu1';
0080 [A,B] = <a href="kalman_transition_matrix.html" class="code" title="function [A,B] = kalman_transition_matrix(dr)">kalman_transition_matrix</a>(dr);
0081 <span class="comment">% index of predetermined variables in A</span>
0082 i_pred = [nstatic+(1:npred) M_.endo_nbr+1:length(A)];
0083 A = A(i_pred,i_pred);
0084 [vx, ns_var] = <a href="lyapunov_symm.html" class="code" title="function [x,ns_var]=lyapunov_symm(a,b)">lyapunov_symm</a>(A,b);
0085 i_ivar = find(~ismember(ivar,dr.order_var(ns_var+nstatic)));
0086 ivar = ivar(i_ivar);
0087 iky = iv(ivar);
0088 aa = ghx(iky,:);
0089 bb = ghu(iky,:);
0090 Gamma = zeros(nvar,cutoff+1);
0091 tmp = aa*vx*aa'+ bb*M_.Sigma_e*bb';
0092 k = find(abs(tmp) &lt; 1e-12);
0093 tmp(k) = 0;
0094 Gamma(:,1) = diag(tmp);
0095 vxy = (A*vx*aa'+ghu1*M_.Sigma_e*bb');
0096 tmp = aa*vxy;
0097 k = find(abs(tmp) &lt; 1e-12);
0098 tmp(k) = 0;
0099 Gamma(:,2) = diag(tmp);
0100 <span class="keyword">for</span> i=2:cutoff
0101 vxy = A*vxy;
0102 tmp = aa*vxy;
0103 k = find(abs(tmp) &lt; 1e-12);
0104 tmp(k) = 0;
0105 Gamma(:,i+1) = diag(tmp);
0106 <span class="keyword">end</span>
0107 H = 1:cutoff;
0108 <span class="keyword">for</span> i=1:nvar
0109 f(i,:) = Gamma(i,1)/(2*pi) + Gamma(i,H+1)*cos(H'*omega')/pi;
0110 <span class="keyword">end</span>
0111
0112 <span class="keyword">if</span> sscanf(version(<span class="string">'-release'</span>),<span class="string">'%d'</span>) &lt; 13
0113 warning on
0114 <span class="keyword">else</span>
0115 eval(<span class="string">'warning on MATLAB:dividebyzero'</span>)
0116 <span class="keyword">end</span>
0117
0118 <span class="keyword">if</span> pltinfo
0119 <span class="keyword">for</span> i= 1:nvar
0120 figure(<span class="string">'Name'</span>,[<span class="string">'Spectral Density of '</span> deblank(M_.endo_names(ivar(i),:)) <span class="string">'.'</span>])
0121 plot(omega,f(i,:),<span class="string">'-k'</span>,<span class="string">'linewidth'</span>,2)
0122 xlabel(<span class="string">'0 \leq \omega \leq \pi'</span>)
0123 ylabel(<span class="string">'f(\omega)'</span>)
0124 box on
0125 axis tight
0126 <span class="keyword">end</span>
0127 <span class="keyword">end</span></pre></div>
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