On 06/10/2020 11:00 a.m., Sorkin, John wrote:
Colleagues,
I am trying to learn to use uniroot to solve a simple linear equation. I define
the function, prove the function and a call to the function works. When I try
to use uniroot to solve the equation I get an error message,
Error in yfu n(x,10,20) : object 'x' not found.
I hope someone can tell we how I can fix the problem
if(!require(rootSolve)){install.packages("rootSolve")}
library(rootSolve)
# Define the function
yfun <- function(x,diffMean,diffSE) ((abs(diffMean)-x)/diffSE)
# Prove the function and a call to the function work
yfun(10,100,10)
# use uniroot to find a solution to the
# function in the range -100 to 100
uniroot(yfun(x,10,20),c(-100,100))
My output:
# Define the function
yfun <- function(x,diffMean,diffSE) ((abs(diffMean)-x)/diffSE)
# Prove the function and a call to the funciton works
yfun(10,100,10)
[1] 9
# use uniroot to find a solution to the
# funciton in the range -100 to 100
uniroot(yfun(x,10,20),c(-100,100))
Error in yfun(x, 10, 20) : object 'x' not found
The problem is that uniroot() wants a function as first argument, and
yfun(x,10,20) is not a function, it's the value of a function. You can
do it with
uniroot(function(x) yfun(x,10,20),c(-100,100))
which creates the anonymous function
function(x) yfun(x,10,20)
and passes that to uniroot().
Duncan Murdoch
Thank you,
John
John David Sorkin M.D., Ph.D.
Professor of Medicine
Chief, Biostatistics and Informatics
University of Maryland School of Medicine Division of Gerontology and Geriatric
Medicine
Baltimore VA Medical Center
10 North Greene Street
GRECC (BT/18/GR)
Baltimore, MD 21201-1524
(Phone) 410-605-7119
(Fax) 410-605-7913 (Please call phone number above prior to faxing)
[[alternative HTML version deleted]]
______________________________________________
R-help@r-project.org 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.
______________________________________________
R-help@r-project.org 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.
