
<A NAME=COEFF>

<TITLE>COEFF</TITLE></A>
<b><a href=r37_idx.html>INDEX</a></b><p><p>



<B>COEFF</B> _ _ _  _ _ _  _ _ _  _ _ _ <B>operator</B><P>
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The <em>coeff</em> operator returns the coefficients of the powers of the 
specified variable in the given expression, in a 
<A HREF=r37_0053.html>list</A>. 
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 <P> <H3> 
syntax: </H3>
<em>coeff</em>(&lt;expression&gt;<em>,</em>&lt;variable&gt;) 
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&lt;expression&gt; is expected to be a polynomial expression, not a rational 
expression. Rational expressions are accepted when the switch 

<A HREF=r37_0322.html>ratarg</A> is on. &lt;variable&gt; must be a kernel. The r
esults are 
returned in a list. 
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 <P> <H3> 
examples: </H3>
<P><PRE><TT>
coeff((x+y)**3,x); 

    3     2
  {Y  ,3*Y  ,3*Y,1} 


coeff((x+2)**4 + sin(x),x); 

  {SIN(X) + 16,32,24,8,1} 


high_pow; 

  4 


low_pow; 

  0 


ab := x**9 + sin(x)*x**7 + sqrt(y); 
 


                          7     9
  AB := SQRT(Y) + SIN(X)*X   + X


coeff(ab,x); 

  {SQRT(Y),0,0,0,0,0,0,SIN(X),0,1}

</TT></PRE><P>The variables 
<A HREF=r37_0010.html>high_pow</A> and 
<A HREF=r37_0013.html>low_pow</A> are set to the 
highest and lowest powers of the variable, respectively, appearing in the 
expression. 
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The coefficients are put into a list, with the coefficient of the lowest 
(constant) term first. You can use the usual list access methods 
(<em>first</em>, <em>second</em>, <em>third</em>, <em>rest</em>, <em>length</em>
, and 
<em>part</em>) to extract them. If a power does not appear in the 
expression, the corresponding element of the list is zero. Terms involving 
functions of the specified variable but not including powers of it (for 
example in the expression <em>x**4 + 3*x**2 + tan(x)</em>) are placed in the 
constant term. 
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Since the <em>coeff</em> command deals with the expanded form of the expression,
 
you may get unexpected results when 
<A HREF=r37_0284.html>exp</A> is off, or when 

<A HREF=r37_0287.html>factor</A> or 
<A HREF=r37_0296.html>ifactor</A> are on. 
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If you want only a specific coefficient rather than all of them, use the 

<A HREF=r37_0142.html>coeffn</A> operator. 
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