[R] Solving quadratic equation in R

Diviya Smith
Thu, 26 Jul 2012 21:17:13 -0000

On Thu, Jul 26, 2012 at 5:16 PM, Diviya Smith
<diviya.smith@gmail.com>wrote:

> Thank you for pointing me to the uniroot function?
>
> Is there a way to constrain this solution so that it only gives me values
> of 'a' between c(0,1)?
>
> I tried using nlminb and for some reason it always estimates a = 0, even
> when I change the objective function.
>
> f <- function(vals) {
>
> x <- vals[1]
>
> sum(c(x^2-x-8.013)^2)
>
> }
>
> nlminb(c(0.05),f, lower=0.00, upper=1.00)
>
>
>
> On Thu, Jul 26, 2012 at 5:00 PM, 辜质敏 <gggzhm@gmail.com> wrote:
>
>> I think it's impossible for 'a' between c(0,1) to satisfy
that
>>
>> a^2 - a = 8.313
>> Without the restraint, you can try following lines to get roots:
>>
>>
>> fun=function(a) a^2-a-8.313
>>
>> root1=uniroot(fun,c(3,4))
>>
>> root2=uniroot(fun,c(-3,-2))
>>
>> Eric
>>
>> On Thu, Jul 26, 2012 at 4:49 PM, Diviya Smith
<diviya.smith@gmail.com>wrote:
>>
>>> Sorry it is important for me to constrain the value of 'a'
between c(0,1)
>>>
>>> On Thu, Jul 26, 2012 at 4:48 PM, Diviya Smith
<diviya.smith@gmail.com
>>> >wrote:
>>>
>>> > Hi there,
>>> >
>>> > I would like to solve a simple equation in R
>>> >
>>> > a^2 - a = 8.313
>>> >
>>> > There is no real solution to this problem but I would like to
get an
>>> > approximate numerical solution. Can someone suggest how I can
set this
>>> up?
>>> >
>>> > Thanks in advance,
>>> > Diviya
>>> >
>>>
>>>         [[alternative HTML version deleted]]
>>>
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>>
>>