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rderivative

multivariable derivative in R

Could somebody help me with simple mathematic operation in R?

All I want to do is:

I have a function

f <-(a1*x1+a2*x2+…+an*xn~x1&…&xn)

and derivative of this function

df<-D(f(x1…xn)~…)

What I need to fill in the '…' gap to obtain a result of multivariable derivative? The problem is that I can't address to value of vector c(x1,x2,x3…xn)

As a result I need to write a "for"-cycle on each step of which it gets me a result of derivative

Solution

  • Do you have a fixed n? If so, you can use parse to transform a string in an expression:

    x = c('x1','x2','x3')
a = c('a1','a2','a3')
expr=parse(text=paste(paste(x, a, sep="*"), collapse="+"))

#> sapply(x, function(u) D(expr,u))
#$x1
#a1

#$x2
#a2

#$x3
#a3