Hi all, I need to solve this following equation which the unknown value (here is "a") is on the exponent place, could anybody please help me to figure it out? I tried to use lm.sol() or solve() function but it doesn't work...... Thanks for help, Peiling (x, y) = (2.21, 1.01) y = 1 + x - ( 1 + (x)^a)^(1/a)
You could probably find a way to do this using nls(), optim() or uniroot() but this seems to be very much a homework problem so I won't say more. solve() solves matrix linear equations... not what you want here. Read the docs. Michael On Thu, May 17, 2012 at 2:53 PM, Pei-Ling Lin <barthealin at gmail.com> wrote:> Hi all, > > I need to solve this following equation which the unknown value (here is "a") is on the exponent place, could anybody please help me to figure it out? I tried to use lm.sol() or solve() function but it doesn't work...... > > Thanks for help, > Peiling > > > ?(x, ? y) = (2.21, 1.01) > > ?y = 1 + x - ( 1 + (x)^a)^(1/a) > > > > ______________________________________________ > R-help at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code.
On Thu, May 17, 2012 at 01:53:39PM -0500, Pei-Ling Lin wrote:> Hi all, > > I need to solve this following equation which the unknown value (here is "a") is on the exponent place, could anybody please help me to figure it out? I tried to use lm.sol() or solve() function but it doesn't work...... > > Thanks for help, > Peiling > > > (x, y) = (2.21, 1.01) > > y = 1 + x - ( 1 + (x)^a)^(1/a)Hi. First, plot the function f <- function(a) { 1 + x - ( 1 + (x)^a)^(1/a) - y } x <- 2.21 y <- 1.01 a <- seq(0.1, 20, length=1000) plot(a, f(a), ylim=c(-0.2, 0.2), type="l") abline(h=0) This suggests, that there is no root. This may also be obtained analytically. Hope this helps. Petr Savicky.