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<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:svg="http://www.w3.org/2000/svg" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:db="http://docbook.org/ns/docbook" version="5.0-subset Scilab" xml:lang="en" xml:id="armax">
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<refname>armax</refname>
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<refpurpose> armax identification</refpurpose>
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<title>Calling Sequence</title>
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<synopsis>[arc,la,lb,sig,resid]=armax(r,s,y,u,[b0f,prf])</synopsis>
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<title>Arguments</title>
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<para>output process y(ny,n); ( ny: dimension of y , n : sample size)</para>
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<para>input process u(nu,n); ( nu: dimension of u , n : sample size)</para>
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<para>auto-regression orders r >=0 et s >=-1</para>
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<para>optional parameter. Its default value is 0 and it means that the coefficient b0 must be identified. if bof=1 the b0 is supposed to be zero and is not identified</para>
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<para>optional parameter for display control. If prf =1, the default value, a display of the identified Arma is given.</para>
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<para>a Scilab arma object (see armac)</para>
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<para>is the list(a,a+eta,a-eta) ( la = a in dimension 1) ; where eta is the estimated standard deviation. , a=[Id,a1,a2,...,ar] where each ai is a matrix of size (ny,ny)</para>
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<para>is the list(b,b+etb,b-etb) (lb =b in dimension 1) ; where etb is the estimated standard deviation. b=[b0,.....,b_s] where each bi is a matrix of size (nu,nu)</para>
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<para>is the estimated standard deviation of the noise and resid=[ sig*e(t0),....] (</para>
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<title>Description</title>
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armax is used to identify the coefficients of a n-dimensional
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<programlisting role=""><![CDATA[
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<refname>armax</refname>
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<refpurpose> armax identification</refpurpose>
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<title>Calling Sequence</title>
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<synopsis>[arc,la,lb,sig,resid]=armax(r,s,y,u,[b0f,prf])</synopsis>
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<title>Arguments</title>
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<para>output process y(ny,n); ( ny: dimension of y , n : sample size)</para>
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<para>input process u(nu,n); ( nu: dimension of u , n : sample size)</para>
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<para>auto-regression orders r >=0 et s >=-1</para>
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<para>optional parameter. Its default value is 0 and it means that the coefficient b0 must be identified. if bof=1 the b0 is supposed to be zero and is not identified</para>
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<para>optional parameter for display control. If prf =1, the default value, a display of the identified Arma is given.</para>
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<para>a Scilab arma object (see armac)</para>
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<para>is the list(a,a+eta,a-eta) ( la = a in dimension 1) ; where eta is the estimated standard deviation. , a=[Id,a1,a2,...,ar] where each ai is a matrix of size (ny,ny)</para>
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<para>is the list(b,b+etb,b-etb) (lb =b in dimension 1) ; where etb is the estimated standard deviation. b=[b0,.....,b_s] where each bi is a matrix of size (nu,nu)</para>
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<para>is the estimated standard deviation of the noise and resid=[ sig*e(t0),....] (</para>
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<title>Description</title>
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armax is used to identify the coefficients of a n-dimensional
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<programlisting role=""><![CDATA[
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A(z^-1)y= B(z^-1)u + sig*e(t)
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]]></programlisting>
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where e(t) is a n-dimensional white noise with variance I.
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sig an nxn matrix and A(z) and B(z):
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<programlisting role=""><![CDATA[
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where e(t) is a n-dimensional white noise with variance I.
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sig an nxn matrix and A(z) and B(z):
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<programlisting role=""><![CDATA[
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A(z) = 1+a1*z+...+a_r*z^r; ( r=0 => A(z)=1)
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B(z) = b0+b1*z+...+b_s z^s ( s=-1 => B(z)=0)
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]]></programlisting>
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for the method see Eykhoff in trends and progress in system identification, page 96.
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<literal>z(t)=[y(t-1),..,y(t-r),u(t),...,u(t-s)]</literal>
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<literal>coef= [-a1,..,-ar,b0,...,b_s] </literal>
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<literal>y(t)= coef* z(t) + sig*e(t) </literal> and the algorithm minimises
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<literal>sum_{t=1}^N ( [y(t)- coef'z(t)]^2)</literal>
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where t0=max(max(r,s)+1,1))).
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<title>Examples</title>
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<programlisting role="example"><![CDATA[
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for the method see Eykhoff in trends and progress in system identification, page 96.
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<literal>z(t)=[y(t-1),..,y(t-r),u(t),...,u(t-s)]</literal>
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<literal>coef= [-a1,..,-ar,b0,...,b_s] </literal>
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<literal>y(t)= coef* z(t) + sig*e(t) </literal> and the algorithm minimises
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<literal>sum_{t=1}^N ( [y(t)- coef'z(t)]^2)</literal>
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where t0=max(max(r,s)+1,1))).
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<title>Examples</title>
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<programlisting role="example"><![CDATA[
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//-Ex1- Arma model : y(t) = 0.2*u(t-1)+0.01*e(t-1)
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ny=1,nu=1,sig=0.01;
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Arma=armac(1,[0,0.2],[0,1],ny,nu,sig) //defining the above arma model