Performs a Peto-Peto nonparametric test of differences in cdfs between groups. If more than two groups, the test is followed by a nonparametric multiple comparison test. Uses the BH method of adjusting p-values.
cen1way(x1, x2, group, mcomp.method = "BH", printstat = TRUE)The column of data values plus detection limits
The column of indicators, where 1 (or TRUE) indicates a detection limit in the y1 column, and 0 (or FALSE) indicates a detected value in y1.
Grouping or factor variable. Can be either a text or numeric value indicating the group assignment.
One of the standard methods for adjusting p-values for multiple comparisons. Type ?p.adjust for the list of possible methods. Default is Benjamini-Hochberg "BH" false discover rate.
Logical TRUE/FALSE option of whether to print the resulting statistics in the console window, or not. Default is TRUE.
A list of summary statistics for each group evaluated containing the following components:
N Number of samples
PctND Percentage of non-detects
KMmean Kaplan-Meier estimate of the mean
KMsd Kaplan-Meier estimate of standard deviation
KMmedian Kaplan-Meier estmate of the median
Peto-Peto test results including Chi-Squared value, degrees of freedom and p-value of the test.
If more than two groups, p-values of the pairwise multiple comparisons, adjusted using the BH false-discovery rate, are reported.
Helsel, D.R., 2011. Statistics for Censored Environmental Data using Minitab and R, 2nd ed. John Wiley & Sons, USA, N.J.
Peto, R., Peto, J., 1972. Asymptotically Efficient Rank Invariant Test Procedures. Journal of the Royal Statistical Society. Series A (General) 135, 185. doi: 10.2307/2344317
Benjamini, Y., Hochberg, Y., 1995. Controlling the False Discovery Rate: A Practical and Powerful Approach to Multiple Testing. Journal of the Royal Statistical Society. Series B (Methodological), 57, 289-300.
data(PbHeron)
# Two Groups
cen1way(PbHeron$Liver,PbHeron$LiverCen,PbHeron$DosageGroup)
#> Warning: One or more group(s) do not have censored data.
#> grp N PctND Mean SD LCLmean
#> 1 High 13 0.00 9.2880 16.39000 -0.6188
#> 2 Low 14 28.57 0.1202 0.09919 0.0758
#>
#> Oneway Peto-Peto test of CensData: PbHeron$Liver by Factor: PbHeron$DosageGroup
#> Chisq = 7.388 on 1 degrees of freedom p = 0.00657
# More than two groups
cen1way(PbHeron$Liver,PbHeron$LiverCen,PbHeron$Group)
#> Warning: One or more group(s) do not have censored data.
#> Warning: One or more group(s) do not have censored data.
#> grp N PctND KMmean KMsd LCLmean
#> 1 1 7 28.57 0.1020 0.08834 0.03338
#> 2 2 7 28.57 0.1384 0.10590 0.07153
#> 3 3 6 0.00 12.1100 16.16000 -4.84900
#> 4 4 7 0.00 6.8660 17.46000 -9.28600
#>
#> Oneway Peto-Peto test of CensData: PbHeron$Liver by Factor: PbHeron$Group
#> Chisq = 7.795 on 3 degrees of freedom p = 0.0504
#>
#> Pairwise comparisons using Peto & Peto test
#>
#> data: CensData and Factor
#>
#> 1 2 3
#> 2 0.887 - -
#> 3 0.171 0.321 -
#> 4 0.079 0.127 0.887
#>
#> P value adjustment method: BH