Hi,
I am stuck on something for a couple days, I am almost about to give up.
This looks simple, but I can't figure out. I hope I can get some help here.
I am trying to do some symbolic and numerical derivations. Let me explain
the problem. Let's say, I have a matrix as follows:
> load <- matrix(c(3,0,1,4,1,3),nrow=3,ncol=2,byrow=TRUE)
>
> load
[,1] [,2]
[1,] 3 0
[2,] 1 4
[3,] 1 3
I will create objects for each element of the matrix, and assign the matrix
elements to these objects. These objects will be also an element of another
matrix.
l <- matrix(nrow=nrow(load),ncol=ncol(load))
for(i in 1:nrow(load)) {
for(j in 1:ncol(load)) { l[i,j]=paste("l",i,j,sep="")}}
> l
[,1] [,2]
[1,] "l11" "l12"
[2,] "l21" "l22"
[3,] "l31" "l32"
> l11
[1] 3
> l12
[1] 0
> l21
[1] 1
> l22
[1] 4
> l31
[1] 1
> l32
[1] 3
Let's say, I need to take the derivative of (l11*l21+l12*l22) with respect
to l11,l12,l21,l22,l31,l32.
> numericDeriv(quote(l11*l21+l12*l22), c(t(l),recursive=TRUE))
[1] 3
attr(,"gradient")
[,1] [,2] [,3] [,4] [,5] [,6]
[1,] 1 4 3 0 0 0
Everything is fine up to this point. I need what I have. But, I don't want
to manipulate the elements in "quote()" manually within the numericDeriv
function. For instance, I want to call these elements from the matrix "l"
as below:
> a <- paste(
+ paste(l[1,1],l[2,1],sep="*"),
+ paste(l[1,2],l[1,2],sep="*"),
+ sep="+"
+ )
> a
[1] "l11*l21+l12*l12"
Now, "a" is a character. Do you have any idea about how to use the
character value "l11*l21+l12*l12" assigned to object "a" within the
numericDeriv function. So, I can get the same result as above without
manipulating the expression in quote() manually.
Thanks
--
Cengiz Zopluoglu
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