R help - Sep 2000 - D function

Dear R People:

Suppose I put in the following:
> w1 <- expression(2*x)
> v1 <- expression(x^2)
and I want to get the derivative of w1 * v1 with respect to
x
> D(w1*v1,"x")
Error in w1 * v1 : non-numeric argument to binary operator


Is there a way around this, please?

Thanks in advance!

Sincerely,
Erin M. Hodgess, Ph.D.
Associate Professor
Department of Computer and Mathematical Sciences
University of Houston - Downtown
One Main Street 
Houston, TX 77002
e-mail: hodgess at uhddx01.dt.uh.edu


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Erin Hodgess <hodgess at uhddx01.dt.uh.edu> writes:
> Suppose I put in the following:
> 
> > w1 <- expression(2*x)
> > v1 <- expression(x^2)
> 
> and I want to get the derivative of w1 * v1 with respect to x
> > D(w1*v1,"x")
> Error in w1 * v1 : non-numeric argument to binary operator
> Is there a way around this, please?
You need to create a single expression that does not refer to w1 and
v1.
> D(expression((2 * x) * (x * 2)), "x")
2 * (x * 2) + (2 * x) * 2
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r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at
stat.math.ethz.ch
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