I have a function which is actually an output of another function and I
therefore cannot change it. I am trying to use *multiroot * from package *rootSolve * to compute the roots of the function but its not working at all. Is there something I am not seeing or is there another alternative that is based on Newton-Raphson technique? library(rootSolve) f <- function(q,m){ c(F1 = 12 * ((exp(q[, 1]) * m[1])/(exp(q[, 1]) * m[1] + exp(q[, 2]) * m[2] + m[3])) - c(1,2), F2 = 12 * ((exp(q[, 2]) * m[2])/(exp(q[, 1]) * m[1] + exp(q[, 2]) * m[2] + m[3])) - c(3,3)) } m = c(0.1,0.2,0.7) I am trying to solve for *q* and from based on the given m, I expect something like this; q <- matrix(c(-0.1335314,0.6931472,0.2719337,0.4054651), nrow=2) How would I call the multiroot for the function f to hopefully get the above results. I thought of using newtonRaphson from package pracma but that possibly only handles univariate inputs. [[alternative HTML version deleted]] ______________________________________________ [hidden email] mailing list -- To UNSUBSCRIBE and more, see 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. |
Forgot to send this to R-help. You have already asked this question on stackoverflow (https://stackoverflow.com/questions/64835251/how-can-i-use-multiroot-with-matrix-based-functions-in-r/64835725#64835725). In a comment G. Grothendieck provided an answer. Have you tried it? Define a function f.mod that converts a vector to a matrix like this f.mod <- function(q,m) f(matrix(q,2),m) Then try multiroot with an appropriate starting value q.start <- rep(0,4) multiroot(f.mod, q.start, parms=m) Finally convert the answer provided by multiroot to a matrix. You can also use other solvers. Such as nleqslv like this library(nleqslv) nleqslv(q.start,f.mod,m=m) # uses Broyden nleqslv(q.start,f.mod,m=m,method="Newton") # uses Newton The second call of nleqslv uses less iterations that multiroot. You can check the answers. Berend Hasselman > On 17 Nov 2020, at 09:19, quinter sam <[hidden email]> wrote: > > I have a function which is actually an output of another function and I > therefore cannot change it. I am trying to use *multiroot * from > package *rootSolve > * to compute the roots of the function but its not working at all. Is there > something I am not seeing or is there another alternative that is based on > Newton-Raphson technique? > > library(rootSolve) > f <- function(q,m){ > c(F1 = 12 * ((exp(q[, 1]) * m[1])/(exp(q[, 1]) * m[1] + exp(q[, 2]) * m[2] > + m[3])) - c(1,2), > F2 = 12 * ((exp(q[, 2]) * m[2])/(exp(q[, 1]) * m[1] + exp(q[, 2]) * m[2] + > m[3])) - c(3,3)) > } > m = c(0.1,0.2,0.7) > > I am trying to solve for *q* and from based on the given m, I expect > something like this; > q <- matrix(c(-0.1335314,0.6931472,0.2719337,0.4054651), nrow=2) > > How would I call the multiroot for the function f to hopefully get the > above results. I thought of using newtonRaphson from package pracma but > that possibly only handles univariate inputs. > > [[alternative HTML version deleted]] > > ______________________________________________ > [hidden email] mailing list -- To UNSUBSCRIBE and more, see > 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. ______________________________________________ [hidden email] mailing list -- To UNSUBSCRIBE and more, see 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. |
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