[R] D function

[Douglas Bates]

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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