Description Usage Arguments Details Value References Examples
Estimate of relative potency of two toxins using Litchfield and Wilcoxon's (1949) approach to evaluating doseeffect experiments.
1  relPotency(ED50nS1, ED50nS2, vec = FALSE)

ED50nS1 
Either the list output from 
ED50nS2 
Either the list output from 
vec 
A logical scalar indicating whether the inputs 
The ratios reported (both for slope and potency) have the first toxin in the numerator and the second toxin in the denominator, but the test results (both for parallelism and relative potency) are based on the ratios of the larger values over the smaller values.
No relative potency is estimated if the two doseeffect curves differ significantly from parallelism (with 95% confidence).
A list with two elements, SR
with three elements:
r
= a numeric vector of length three with the estimated
slope ratio with 95% confidence limits,
f
= a numeric scalar with the f of the slope ratio, and
parallel
= a logical scalar indicating whether the two
curves differ significantly from parallelism (FALSE).
and PR
with one (just difPotency
if parallel=FALSE
)
or three (if parallel=TRUE
) elements:
r
= a numeric vector of length three with the estimated
potency ratio with 95% confidence limits,
f
= a numeric scalar with the f of the potency ratio, and
difPotency
= a logical scalar indicating whether the two
toxins differ significantly in potency (FALSE).
Litchfield, JT Jr. and F Wilcoxon. 1949. A simplified method of evaluating doseeffect experiments. Journal of Pharmacology and Experimental Therapeutics 96(2):99113. [link].
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17  # Example starting from raw tox data
dose < c(0.0625, 0.125, 0.25, 0.5, 1)
ntested < rep(8, 5)
nalive1 < c(1, 4, 4, 7, 8)
mydat1 < dataprep(dose=dose, ntot=ntested, nfx=nalive1)
nalive2 < c(0, 1, 2, 6, 6)
mydat2 < dataprep(dose=dose, ntot=ntested, nfx=nalive2)
fit1 < LWestimate(fitLWauto(mydat1), mydat1)
fit2 < LWestimate(fitLWauto(mydat2), mydat2)
relPotency(fit1, fit2)
# Example from Litchfield and Wilcoxon (1949)
# comparing Tagathen and Pyribenzamine
relPotency(c(0.18, 1.72, 2.20, 1.60), c(0.60, 1.60, 2.34, 1.57), vec=TRUE)
# Example in which curves differ significantly from parallelism.
relPotency(c(0.18, 1.72, 2.20, 1.60), c(0.60, 1.60, 4.34, 1.57), vec=TRUE)

Warning message:
no DISPLAY variable so Tk is not available
$SR
$SR$r
ratio.S lower.S upper.S
0.9832027 0.3450847 2.8013049
$SR$f
fS
2.849163
$SR$parallel
[1] TRUE
$PR
$PR$r
ratio.ED50 lower.ED50 upper.ED50
0.4119745 0.1668644 1.0171309
$PR$f
fED50
2.468917
$PR$difPotency
[1] FALSE
$SR
$SR$r
ratio lower upper
0.9401709 0.4901066 1.8035290
$SR$f
[1] 1.918299
$SR$parallel
[1] TRUE
$PR
$PR$r
ratio lower upper
0.3000000 0.1463695 0.6148822
$PR$f
[1] 2.049607
$PR$difPotency
[1] TRUE
$SR
$SR$r
ratio lower upper
0.5069124 0.2642510 0.9724097
$SR$f
[1] 1.918299
$SR$parallel
[1] FALSE
$PR
$PR$r
ratio lower upper
NA NA NA
$PR$f
[1] NA
$PR$difPotency
[1] NA
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