[R] Dynamically build functional expression and taking derivative
Oleksandr Dyklevych
diklevich at gmail.com
Thu Dec 9 17:59:46 CET 2010
Hi!
I'm faced the next problem:
suppose I have a vector of some coefficient and for some purpose from
these coefficients I need dynamically build a functional expression
(because, the number of elements in the vector of coefficients might
differ each time). So, I'm trying to do like this (let the number of
coefficients be 3):
Building expression
> foo <- gsub(",","*",toString(paste('(p',1:3,'*x +
> (1-p',1:3,'))',sep="")))
> foo
[1] "(p1*x + (1-p1))* (p2*x + (1-p2))* (p3*x + (1-p3))"
But now, how can I take derivative of this expression w.r.t. "x"?
> dfoo <- D(foo,"x") #doesn't work as well as
> dfoo <- D(as.expression(foo),"x")
May be there are other ways to handle this kind of situation?
Best regards,
Oleksandr
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