laurelisse - 8 months ago 56

R Question

I have written a function to approximate a derivate in a point x in R like this:

`nderiv<- function(f,x,h){`

(f(x+h)-f(x))/h

}

And want to make an input in f as either x^2, "x^2" or as a predefined function like:

`ex<- function(x){`

x^2

}

The code works fine if you use the last example (using a predefined function). But I can't get it to work when inserting the other options.

I either get the error

Error in nderiv(x^2, 1) : object 'x' not found

or

Error in nderiv("x^2", 1, 1e-04) : could not find function "f"

So I would like to be able to write

`nderiv(x^2,1,0.0001)`

`nderiv("x^2",1,0.0001)`

Thanks in advance!

Answer

If you want to use `x^2`

as an anonymous function, pass it to `nderiv`

as `function(x){x^2}`

. Something like:

```
nderiv(function(x){x^2}, 1, 0.0001)
```

Source (Stackoverflow)