TTT method for lambda_z estimation [🇷 for BE/BA]

posted by yjlee168 Homepage – Kaohsiung, Taiwan, 2008-09-30 14:34 (5684 d 11:58 ago) – Posting: # 2446
Views: 55,747

Dear DLabes,

We have some initial results for the estimation of lambdaz using TTT method. The following are the output obtained from R console.
b<-c(0,0.25,0.5,0.75,1,1.5,2,3,4,8,12,24)
c<-c(0,30.1,211,1221,1485,1837,1615,1621,1411,763,424,109)
dat <- data.frame(time=b,conc=c)
n_lambda=0
x<-which.max(dat$conc)
TTT<-dat[x,1]*2
for (i in (nrow(dat)-2):(which.max(dat$conc)+1)) {
 if (dat$time[[i]] < TTT) {
    n_lambda <- nrow(dat)-i
  }
 }
dat
    time   conc
1   0.00    0.0
2   0.25   30.1
3   0.50  211.0
4   0.75 1221.0
5   1.00 1485.0
6   1.50 1837.0 <-- Tmax
7   2.00 1615.0
8   3.00 1621.0 <-- Two Tmax Time (TTT)
9   4.00 1411.0
10  8.00  763.0
11 12.00  424.0
12 24.00  109.0
summary(lm(log(conc)~time,dat[(nrow(dat)-n_lambda)+1:nrow(dat),]))

Call:
lm(formula = log(conc) ~ time, data = dat[(nrow(dat) - n_lambda) +
    1:nrow(dat), ])

Residuals:
       8        9       10       11       12  <--- data points selected
 0.06042  0.05031 -0.04997 -0.12297  0.06220

Coefficients:
             Estimate Std. Error t value Pr(>|t|)   
(Intercept)  7.716264   0.071884  107.34 1.78e-06 ***
time        -0.128630   0.005651  -22.76 0.000186 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.09604 on 3 degrees of freedom
  (7 observations deleted due to missingness)
Multiple R-squared: 0.9942,     Adjusted R-squared: 0.9923
F-statistic: 518.1 on 1 and 3 DF,  p-value: 0.0001857

It seems not so difficult to implement TTT method using R. Meanwhile, it is easy to validate visually. Thanks.
—
All the best,
-- Yung-jin Lee
bear v2.9.1:- created by Hsin-ya Lee & Yung-jin Lee
Kaohsiung, Taiwan https://www.pkpd168.com/bear
Download link (updated) -> here
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