Re: How do I assign the solution obtained by FindRoot to a variable?

*To*: mathgroup at smc.vnet.net*Subject*: [mg128488] Re: How do I assign the solution obtained by FindRoot to a variable?*From*: Bob Hanlon <hanlonr357 at gmail.com>*Date*: Wed, 24 Oct 2012 03:33:47 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net*References*: <20121023045437.AE4F2685C@smc.vnet.net>

Plot can be used to help identify starting values for FindRoot eqn = Sin[x] + Exp[x]; z = x /. FindRoot[eqn, {x, 0}] -0.588533 Plot[eqn, {x, -10, 2}, Epilog -> {Red, AbsolutePointSize[4], Point[{z, 0}]}] For negative x, the Sin[x] term will cause the expression to oscillate. Pick some range of interest pts = {x, 0} /. Table[ FindRoot[eqn, {x, -n*Pi}], {n, 0, 12}]; Plot[eqn, {x, -40, 0.75}, Epilog -> {Red, AbsolutePointSize[4], Point[pts]}] eqns = {Exp[x - 2] == y, y^2 == x}; Plot[ Evaluate[y /. Solve[#, y] & /@ eqns], {x, -.5, 2.75}, Frame -> True, Axes -> False] pts = {x, y} /. FindRoot[eqns, {{x, #[[1]]}, {y, #[[2]]}}] & /@ {{0.1, 0.1}, {2.5, 1.5}} {{0.019026, 0.137935}, {2.44754, 1.56446}} Plot[ Evaluate[y /. Solve[#, y] & /@ eqns], {x, -.5, 2.75}, Frame -> True, Axes -> False, Epilog -> {Red, AbsolutePointSize[4], Point[pts]}] You can also use Ted Ersek's Root Search package http://forums.wolfram.com/mathgroup/archive/2012/Apr/msg00444.html Bob Hanlon On Tue, Oct 23, 2012 at 12:55 PM, Nan-Sheng Lin <nansheng.lin at gmail.com> wrote: > Thank you very much for all the responses I received. I did not realize > that I only replied to the sender, and not cc-ing the group. > > Anyway, all the responses have been helpful, and it is clear to me now. I > do have a follow-up question - how do I use FindRoot[] or any other function > to find ALL the roots of a non-polynomial function within a specified range? > > Thanks! > > NS > > On Tue, Oct 23, 2012 at 8:11 AM, Bob Hanlon <hanlonr357 at gmail.com> wrote: >> >> eqn = Sin[x] + Exp[x]; >> >> z = x /. >> FindRoot[eqn, {x, 0}] >> >> -0.588533 >> >> eqn /. x -> z >> >> 0. >> >> eqns = {Exp[x - 2] == y, y^2 == x}; >> >> {r, s} = {x, y} /. >> FindRoot[eqns, >> {{x, 1}, {y, 1}}] >> >> {0.019026, 0.137935} >> >> eqns /. {x -> r, y -> s} >> >> {True, True} >> >> >> Bob Hanlon >> >> >> On Tue, Oct 23, 2012 at 12:54 AM, NS Lin <nansheng.lin at gmail.com> wrote: >> > I would like to store the root/solution obtained by the FindRoot[] >> > function to a variable. How can I do that? >> > >> > Thanks! >> > >> > NS >> > > >

**References**:**How do I assign the solution obtained by FindRoot to a variable?***From:*NS Lin <nansheng.lin@gmail.com>