similar to: plot representation of calculated value known to be 7.4

Dear friends - copy paste missed SID <- c() before the first loop - sorry BW Troels Den 25-12-2017 kl. 19:12 skrev Troels Ring: > > Dear friends - merry Christmas and thanks a lot for much help during > the year! > > In the example below I fail to understand how the calculated value pH > is represented in a simple plot - also included. The calculations are > useful

Thanks a lot - formatting the ordinate as ylim=c(4,10) before plotting pH also removed the problem, and options(digits=10) confirmed that pH was not all exactly 7.4 - as I knew. Still I wonder just why R chooses to plot(ATOT,pH) as shown with repeated "7.4" instead of some more detailed representation. Thanks a gain and happy New Year! Troels Den 26-12-2017 kl. 01:03 skrev Bert

I hope you will forgive me this simple question on titration. I'm trying to find very small values from the algorithm below, which I believe is correctly formatted, and the constants are also correct. When SID goes over ATOT, fitted vales are much too low compared to the literature. I guess I must be using optimize in a wrong way but cannot find out how to improve it. I'm on windows, R

Dear friends - occurring in Windows R2.6.2 I am modeling physical chemistry in collaboration with a friend who has preferred working in Excel. I used uniroot, and find a solution to a two buffer problem in acid-base chemistry which I believe is physiologically sensible. Using "goal seek" in Excel my friend found another plausible root, quite close to zero, and a plot of the function

Dear friends - I have a function for the charge in a fluid (water) buffered with HEPES and otherwise only containing Na and Cl so that [Na] - [Cl] = SID (strong ion difference) goes from -1 mM to 1 mM. With known SID and total HEPES concentration I can calculate accurately the pH if I know 3 pK values for HEPES by finding the single root with uniroot Now, the problem is that there is some

Thanks a lot! This was amazing. I'm not sure I see how the conditiion pK1 < pK2 < pK3 is enforced? - it comes from the derivation via generalized Henderson-Hasselbalch but perhaps it is not really necessary. Anyway, the use of Vectorize did the trick! Best wishes Troels Den 06-11-2023 kl. 19:19 skrev Ivan Krylov: > ? Mon, 6 Nov 2023 17:53:49 +0100 > Troels Ring <tring at

? Mon, 6 Nov 2023 17:53:49 +0100 Troels Ring <tring at gvdnet.dk> ?????: > Hence I wonder if I could somehow have non linear regression to find > the 3 pK values. Below is HEPESFUNC which delivers charge in the > fluid for known pKs, HEPTOT and SID. Is it possible to have > root-finding in the formula with nls? Sure. Just reformulate the problem in terms of a function that

Good afternoon, I have a 63 small .csv files which I process daily, and until two weeks ago they processed just fine and only took a matter of moments and had non noticeable memory problem. Two weeks ago they have reached 318 lines and my script "broke". There are some missing-values in some of the files. I have tried hard many times over the last two weeks to create a

Good morning, I have currently 63 .csv files most of which have lines which look like 01/06/05,23445 Though some files have two numbers beside each date. There are missing values, and currently the longest file has 318 rows. (merge() is losing the head and doing runaway memory allocation - but thats another question - I'm still trying to pin that issue down and make a small repeatable

Good morning! I've searched the docs etc... Am I doing something wrong or is this a bug? I'm doing a merge of two dataframes and getting extra rows in the resulting dataframe - the dataframes being merged might have NAs... count <- 10 nacount <- 3 a1 <- as.data.frame(as.Date("2005-06-01")+0:(count-1)) names(a1) <- "mdate" a1$value <- runif(count)

With main R releases only happening yearly in spring, now is good time to consider *and* discuss new features for what we often call "R-devel" and more officially is R Under development (unstable) (.....) -- "Unsuffered Consequences" Here is one such example I hereby expose to public scrutiny: A few minutes ago, I've committed the following to R-devel (the

Hi all, This is probably a blindingly obvious question: Why does it matter in the uniroot function whether the f() values at the end points that you supply are of the same sign? For example: f <- function(x,y) {y-x^2+1} #this gives a warning uniroot(f,interval=c(-5,5),y=0) Error in uniroot(f, interval=c(-5, 5), y = 0) : f() values at end points not of opposite sign #this doesn't give a

Hi, I have tried to use uniroot to solve a value (value a in my function) that gives f=0, and I repeat this process for 10000 times(stimulations). However error occures from the 4625th stimulation - Error in uniroot(f, c(0, 2), maxiter = 1000, tol = 0.001) : f() values at end points not of opposite sign I have also tried interval of (lower=min(U), upper=max(U)) and it won't work as well.

I wrote first cut at unirootR for Martin M and he revised and put in Rmpfr. The following extends Ben's example, but adds the unirootR with trace output. c1 <- 4469.822 c2 <- 572.3413 f <- function(x) { c1/x - c2/(1-x) }; uniroot(f, c(1e-6, 1)) uniroot(f, c(1e-6, 1)) library(Rmpfr) unirootR(f, c(1e-6, 1), extendInt="no", trace=1) This gives more detail on the iterations,

Le 18/02/2023 ? 21:44, J C Nash a ?crit?: > I wrote first cut at unirootR for Martin M and he revised and put in > Rmpfr. > > The following extends Ben's example, but adds the unirootR with trace > output. > > c1 <- 4469.822 > c2 <- 572.3413 > f <- function(x) { c1/x - c2/(1-x) }; uniroot(f, c(1e-6, 1)) > uniroot(f, c(1e-6, 1)) > library(Rmpfr) >

I am calling the uniroot function from inside another function using these lines (last two lines of the function) : d <- uniroot(k, c(.001, 250), tol=.05) return(d$root) The problem is that on occasion there's a problem with the values I'm passing to uniroot. In those instances uniroot stops and sends a message that it can't calculate the root because f.upper * f.lower is greater

Dear friends - I'm using Tinn-R in Windows and find it OK. My son is running MacOS and is just starting using R and I know nothing about MacOS and R but we seem to have difficulties in finding something similar to Tinn for MaC. What are your suggestions? Thanks a lot! Troels Ring, MD Aalborg, Denmark

Dear friends - below is a subset of a much larger material showing two ways of generating two "lines". The intention is to have the colour reflect a variable, pH, but the legend is disturbed. The little part marked "3" above the colour scale is unwelcome. Why did it appear? How could I avoid it? I'm on Windows 7, R version 3.4.1 (2017-06-30) -- "Single

Hello List does anyone have an R function for the Lambert W function? I need complex arguments. [the Lamert W function W(z) satisfies W(z)*exp(W(z)) = z but I could'nt even figure out how to use uniroot() for complex z] -- Robin Hankin Uncertainty Analyst Southampton Oceanography Centre SO14 3ZH tel +44(0)23-8059-7743 initialDOTsurname at soc.soton.ac.uk (edit in obvious way; spam

Hi, I'm using windows xp and R 2.8.0 - I wonder what is the command to put in a script that has the same effect as when in a plot you choose menu "History" and "Recording". Best wishes Troels -- Troels Ring - - Department of nephrology - - Aalborg Hospital 9100 Aalborg, Denmark - - +45 99326629 - - tring at gvdnet.dk