[R] deriv - accessing numeric output for gradient

From: Rotella, Jay <rotella_at_montana.edu>
Date: Wed 20 Jul 2005 - 09:11:46 EST


Hi,
I am interested in using the numeric output from the "gradient" attribute of deriv's output in subsequent analyses. But, I have so far been unable to determine how to do so.

I will use the example from the deriv help to illustrate.

> ## function with defaulted arguments:
> (fx <- deriv(y ~ b0 + b1 * 2^(-x/th), c("b0", "b1", "th"),

                  function(b0, b1, th, x = 1:7){} ) )
>     fx(2,3,4)

This yields
[1] 4.522689 4.121320 3.783811 3.500000 3.261345 3.060660 2.891905
attr(,"gradient")

     b0 b1 th
[1,] 1 0.8408964 0.1092872
[2,] 1 0.7071068 0.1837984
[3,] 1 0.5946036 0.2318331
[4,] 1 0.5000000 0.2599302
[5,] 1 0.4204482 0.2732180
[6,] 1 0.3535534 0.2756976
[7,] 1 0.2973018 0.2704720

I would greatly appreciate it if anyone could tell me how to convert the numbers listed under "b0", "b1", and "th" into a matrix.

Thanks!

Jay Rotella
Ecology Department
Montana State University
Bozeman, MT 59717

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