R: Simultaneous Tests for Ratios of Means of Multiple Endpoints
SimTestRat
R Documentation
Simultaneous Tests for Ratios of Means of Multiple Endpoints
Description
Simultaneous tests for ratios of contrasts (linear functions) of normal means (e.g.,
"Dunnett", "Tukey", "Williams" ect.) when there is more than one primary response
variable (endpoint). The procedure of Hasler and Hothorn (2012) is applied for
ratios of means of normally distributed data. The covariance matrices (containing
the covariances between the endpoints) may be assumed to be equal or possibly
unequal for the different groups (Hasler, 2014). For the case of only a single
endpoint and unequal covariance matrices (variances), the procedure coincides with
the PI procedure of Hasler and Hothorn (2008).
Usage
SimTestRat(data, grp, resp = NULL, type = "Dunnett", base = 1, Num.Contrast = NULL,
Den.Contrast = NULL, alternative = "two.sided", Margin = NULL,
covar.equal = FALSE)
Arguments
data
a data frame containing a grouping variable and the endpoints as
columns
grp
a character string with the name of the grouping variable
resp
a vector of character strings with the names of the endpoints; if
resp=NULL (default), all column names of the data frame
without the grouping variable are chosen automatically
type
a character string, defining the type of contrast, with the following
options:
"Dunnett": many-to-one comparisons, with control in the
denominator
"Tukey": all-pair comparisons
"Sequen": comparisons of consecutive groups, where the group
with lower order is the denomniator
"AVE": comparison of each group with average of all others,
where the average is taken as denominator
"GrandMean": comparison of each group with grand mean of all
groups, where the grand mean is taken as
denominator
"Changepoint": ratios of averages of groups of higher order
divided by averages of groups of lower order
"Marcus": Marcus contrasts as ratios
"McDermott": McDermott contrasts as ratios
"Williams": Williams contrasts as ratios
"UmbrellaWilliams": Umbrella-protected Williams contrasts as
ratios
note that type is ignored if Num.Contrast and
Den.Contrast are specified by the user (see below)
base
a single integer specifying the control (i.e. denominator) group for
Dunnett contrasts, ignored otherwise
Num.Contrast
a numerator contrast matrix, where columns correspond to
groups and rows correspond to contrasts
Den.Contrast
a denominator contrast matrix, where columns correspond to
groups and rows correspond to contrasts
alternative
a character string specifying the alternative hypothesis,
must be one of "two.sided" (default), "greater"
or "less"
Margin
a single numeric value, or a numeric vector corresponding to
endpoints, or a matrix where columns correspond to endpoints and
rows correspond to contrasts, default is 1
covar.equal
a logical variable indicating whether to treat the covariance
matrices (containing the covariances between the endpoints)
for the different groups as being equal;
if TRUE then the pooled covariance matrix is used,
otherwise the Satterthwaite approximation to the degrees of
freedom is used according to Hasler and Hothorn (2008)
Details
The interest is in simultaneous tests for several ratios of linear combinations
(contrasts) of treatment means in a one-way ANOVA model, and simultaneously for
multiple endpoints. For example, the all-pair comparison of Tukey (1953) and the
many-to-one comparison of Dunnett (1955) for ratios of means are implemented, but
allowing for multiple endpoints. Also, the user is free to create other interesting
problem-specific contrasts. An approximate multivariate t-distribution is
used to calculate (adjusted) p-values (see Hasler and Hothorn, 2012). This
approach controls the familywise error rate in an admissible range and in the
strong sense. The covariance matrices of the treatment groups (containing the
covariances between the endpoints) can be assumed to be equal
(covar.equal=TRUE) or unequal (covar.equal=FALSE). If being equal,
the pooled covariance matrix is used, otherwise approximations to the degrees of
freedom (Satterthwaite, 1946) are used (see Hasler, 2014). Unequal covariance
matrices occure if variances or correlations of some endpoints differ depending on
the treatment groups.
Value
An object of class SimTest containing:
estimate
a matrix of estimated ratios
statistic
a matrix of the calculated test statistics
p.val.raw
a matrix of raw p-values
p.val.adj
a matrix of p-values adjusted for multiplicity
CorrMatDat
either the estimated common correlation matrix of the data
(covar.equal=TRUE) or the list of the different (one for
each treatment) estimated correlation matrices of the data
(covar.equal=FALSE)
CorrMatComp
the estimated correlation matrix to be used for the multivariate
t-distribution
degr.fr
either a single degree of freedom (covar.equal=TRUE) or a
vector of degrees of freedom (covar.equal=FALSE) related
to the comparisons
Note
All measurement objects of each treatment group must have values for each endpoint.
If there are missing values then the procedure stops. If covar.equal=TRUE,
then the number of endpoints must not be greater than the total sample size minus
the number of treatment groups. If covar.equal=FALSE, the number of endpoints
must not be greater than the minimal sample size minus 1. Otherwise the procedure
stops.
All hypotheses are tested with the same test direction for all comparisons and
endpoints (alternative="..."). In case of doubt, use "two.sided".
If Margin is a single numeric value or a numeric vector, then the same
value(s) are used for the remaining comparisons or endpoints. If Margin is
not specified, the default is 1.
Author(s)
Mario Hasler
References
Hasler, M. (2014): Multiple contrast tests for multiple endpoints in the presence of
heteroscedasticity. The International Journal of Biostatistics 10, 17–28.
Hasler, M. and Hothorn, L.A. (2012): A multivariate Williams-type trend procedure.
Statistics in Biopharmaceutical Research 4, 57–65.
Hasler, M. and Hothorn, L.A. (2008): Multiple contrast tests in the presence of
heteroscedasticity. Biometrical Journal 50, 793–800.
Dilba, G. et al. (2006): Simultaneous confidence sets and confidence intervals for
multiple ratios. Journal of Statistical Planning and Inference 136, 2640–2658.
Satterthwaite, F.E. (1946): An approximate distribution of estimates of variance
components. Biometrics 2, 110–114.
See Also
SimTestDiff, SimCiRat,
SimCiDiff
Examples
# Example 1:
# A comparison of the groups B and H against the standard S, on endpoint
# Thromb.count, assuming unequal variances for the groups, and for ratios of
# means. This is an extension of the well-known Dunnett-test to the case of
# heteroscedasticity and in terms of ratios of means instead of differences.
data(coagulation)
comp1 <- SimTestRat(data=coagulation, grp="Group", resp="Thromb.count",
type="Dunnett", base=3, alternative="greater", covar.equal=FALSE)
comp1
# Example 2:
# A comparison of the groups B and H against the standard S, simultaneously on
# all endpoints, assuming unequal covariance matrices for the groups, and for
# ratios of means. This is an extension of the well-known Dunnett-test to the case
# of heteroscedasticity and multiple endpoints, and in terms of ratios of means
# instead of differences.
data(coagulation)
comp2 <- SimTestRat(data=coagulation, grp="Group", resp=c("Thromb.count","ADP","TRAP"),
type="Dunnett", base=3, alternative="greater", covar.equal=FALSE)
summary(comp2)
Results
R version 3.3.1 (2016-06-21) -- "Bug in Your Hair"
Copyright (C) 2016 The R Foundation for Statistical Computing
Platform: x86_64-pc-linux-gnu (64-bit)
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Type 'license()' or 'licence()' for distribution details.
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Type 'contributors()' for more information and
'citation()' on how to cite R or R packages in publications.
Type 'demo()' for some demos, 'help()' for on-line help, or
'help.start()' for an HTML browser interface to help.
Type 'q()' to quit R.
> library(SimComp)
> png(filename="/home/ddbj/snapshot/RGM3/R_CC/result/SimComp/SimTestRat.Rd_%03d_medium.png", width=480, height=480)
> ### Name: SimTestRat
> ### Title: Simultaneous Tests for Ratios of Means of Multiple Endpoints
> ### Aliases: SimTestRat
> ### Keywords: htest
>
> ### ** Examples
>
> # Example 1:
> # A comparison of the groups B and H against the standard S, on endpoint
> # Thromb.count, assuming unequal variances for the groups, and for ratios of
> # means. This is an extension of the well-known Dunnett-test to the case of
> # heteroscedasticity and in terms of ratios of means instead of differences.
>
> data(coagulation)
>
> comp1 <- SimTestRat(data=coagulation, grp="Group", resp="Thromb.count",
+ type="Dunnett", base=3, alternative="greater", covar.equal=FALSE)
> comp1
Test for ratios of means of multiple endpoints
Assumption: Heterogeneous covariance matrices for the groups
Alternative hypotheses: True ratios greater than the margins
comparison endpoint margin estimate statistic p.value.raw p.value.adj
1 B/S Thromb.count 1 1.139 1.3327 0.0997 0.1778
2 H/S Thromb.count 1 1.050 0.4244 0.3382 0.5224
>
> # Example 2:
> # A comparison of the groups B and H against the standard S, simultaneously on
> # all endpoints, assuming unequal covariance matrices for the groups, and for
> # ratios of means. This is an extension of the well-known Dunnett-test to the case
> # of heteroscedasticity and multiple endpoints, and in terms of ratios of means
> # instead of differences.
>
> data(coagulation)
>
> comp2 <- SimTestRat(data=coagulation, grp="Group", resp=c("Thromb.count","ADP","TRAP"),
+ type="Dunnett", base=3, alternative="greater", covar.equal=FALSE)
> summary(comp2)
Numerator contrast matrix:
B H S
B/S 1 0 0
H/S 0 1 0
Denominator contrast matrix:
B H S
B/S 0 0 1
H/S 0 0 1
Estimated covariance matrices of the data:
$B
Thromb.count ADP TRAP
Thromb.count 0.0626 0.0565 -0.0102
ADP 0.0565 0.0638 0.0054
TRAP -0.0102 0.0054 0.0963
$H
Thromb.count ADP TRAP
Thromb.count 0.0943 0.0637 0.0663
ADP 0.0637 0.0518 0.0446
TRAP 0.0663 0.0446 0.1157
$S
Thromb.count ADP TRAP
Thromb.count 0.0318 0.0132 0.0598
ADP 0.0132 0.0079 0.0269
TRAP 0.0598 0.0269 0.1376
Estimated correlation matrices of the data:
$B
Thromb.count ADP TRAP
Thromb.count 1.0000 0.8937 -0.1314
ADP 0.8937 1.0000 0.0687
TRAP -0.1314 0.0687 1.0000
$H
Thromb.count ADP TRAP
Thromb.count 1.0000 0.9121 0.6348
ADP 0.9121 1.0000 0.5770
TRAP 0.6348 0.5770 1.0000
$S
Thromb.count ADP TRAP
Thromb.count 1.0000 0.8338 0.9033
ADP 0.8338 1.0000 0.8161
TRAP 0.9033 0.8161 1.0000
Estimated correlation matrix of the comparisons:
[,1] [,2] [,3] [,4] [,5] [,6]
[1,] 1.0000 0.8494 0.3122 0.2833 0.1708 0.3755
[2,] 0.8494 1.0000 0.2387 0.1335 0.1158 0.1917
[3,] 0.3122 0.2387 1.0000 0.3417 0.2232 0.5550
[4,] 0.2833 0.1335 0.3417 1.0000 0.8869 0.7054
[5,] 0.1708 0.1158 0.2232 0.8869 1.0000 0.5818
[6,] 0.3755 0.1917 0.5550 0.7054 0.5818 1.0000
Alternative hypotheses: True ratios greater than the margins
comparison endpoint margin estimate statistic p.value.raw p.value.adj
1 B/S Thromb.count 1 1.139 1.3327 0.0997 0.3203
2 B/S ADP 1 1.262 2.6398 0.0106 0.0430
3 B/S TRAP 1 1.145 0.7402 0.2337 0.5877
4 H/S Thromb.count 1 1.050 0.4244 0.3382 0.7294
5 H/S ADP 1 1.104 1.1949 0.1258 0.3748
6 H/S TRAP 1 1.098 0.4894 0.3147 0.7018
>
>
>
>
>
> dev.off()
null device
1
>