The atable package supports the analysis and reporting of controlled
clinical trials. Reporting of clinical trials is such a frequent task
that guidelines have been written which recommend certain properties of
clinical trial reports (Moher et al. (2010)). In particular Item 17a of
CONSORT states that “Trial results are often more clearly displayed in
a table rather than in the text”. And Item 15 suggests: “a table
showing baseline demographic and clinical characteristics for each
group”. The atable package is specifically designed to comply with
these two items.
Load the package
library(atable)
# remotes::install_github("arminstroebel/atable") # development versionWe will use the arthritis data set to demonstrate the features of
atable, but as all variables are numeric in arthritis, we add some
other variable types.
data(arthritis, package = "multgee")
arthritis <- within(arthritis, {
score <- ordered(y)
baselinescore <- ordered(baseline)
time <- paste0("Month ", time)
sex <- factor(sex, levels = c(1,2), labels = c("female", "male"))
trt <- factor(trt, levels = c(1,2), labels = c("placebo", "drug"))
date <- as.Date("2016-03-09") + runif(nrow(arthritis), -300, 300)
})To create a summary table of sex and age:
atable_options(format_to = "Console") # more on this in a moment
atable(arthritis, target_cols = c("sex", "age"))
## Group value
## 1 Observations
## 2 906
## 3 sex
## 4 female 27% (249)
## 5 male 73% (657)
## 6 missing 0% (0)
## 7 age
## 8 Mean (SD) 50 (11)
## 9 valid (missing) 906 (0)We can also get statistics grouped by some variable (e.g. a treatment indicator):
atable(arthritis, target_cols = c("sex", "age"), group_col = "trt")
## Warning in stats::ks.test(x, y, alternative = c("two.sided"), ...): p-value will be approximate in
## the presence of ties
## Group placebo drug p stat Effect Size (CI)
## 1 Observations
## 2 447 459
## 3 sex
## 4 female 29% (129) 26% (120) 0.4 0.71 1.1 (0.85; 1.6)
## 5 male 71% (318) 74% (339)
## 6 missing 0% (0) 0% (0)
## 7 age
## 8 Mean (SD) 51 (11) 50 (11) 0.043 0.092 0.058 (-0.072; 0.19)
## 9 valid (missing) 447 (0) 459 (0)Furthermore, we can split by another variable (e.g. timepoints):
atable(arthritis, target_cols = c("sex", "age"), group_col = "trt", split_cols = "time")
## Warning in stats::ks.test(x, y, alternative = c("two.sided"), ...): p-value will be approximate in
## the presence of ties
## Warning in stats::ks.test(x, y, alternative = c("two.sided"), ...): p-value will be approximate in
## the presence of ties
## Warning in stats::ks.test(x, y, alternative = c("two.sided"), ...): p-value will be approximate in
## the presence of ties
## Group placebo drug p stat Effect Size (CI)
## 1 Month 1
## 2 Observations
## 3 149 153
## 4 sex
## 5 female 29% (43) 26% (40) 0.69 0.16 1.1 (0.67; 2)
## 6 male 71% (106) 74% (113)
## 7 missing 0% (0) 0% (0)
## 8 age
## 9 Mean (SD) 51 (11) 50 (11) 0.55 0.092 0.058 (-0.17; 0.28)
## 10 valid (missing) 149 (0) 153 (0)
## 11 Month 3
## 12 Observations
## 13 149 153
## 14 sex
## 15 female 29% (43) 26% (40) 0.69 0.16 1.1 (0.67; 2)
## 16 male 71% (106) 74% (113)
## 17 missing 0% (0) 0% (0)
## 18 age
## 19 Mean (SD) 51 (11) 50 (11) 0.55 0.092 0.058 (-0.17; 0.28)
## 20 valid (missing) 149 (0) 153 (0)
## 21 Month 5
## 22 Observations
## 23 149 153
## 24 sex
## 25 female 29% (43) 26% (40) 0.69 0.16 1.1 (0.67; 2)
## 26 male 71% (106) 74% (113)
## 27 missing 0% (0) 0% (0)
## 28 age
## 29 Mean (SD) 51 (11) 50 (11) 0.55 0.092 0.058 (-0.17; 0.28)
## 30 valid (missing) 149 (0) 153 (0)The same can be achieved via the formula interface:
atable(sex + age ~ trt | time, arthritis)Here, the left hand side represents the variables being summarized. The
right hand side gives the variables being used to group and split the
variables. The variables used to split come after a | character
In an earlier code chunk, we set atable_options(format_to = "Console"). atable is designed to return output in a format optimized
for LaTeX, the console, MS Word (via flextable and officer), HTML or
raw (i.e. no formatting). This is for easy use in manuscripts.
form <- sex + age ~ trt
atable(form, arthritis, format_to = "Latex") # format to LaTeX
atable(form, arthritis, format_to = "Console") # format to console
atable(form, arthritis, format_to = "HTML") # format to HTML
atable(form, arthritis, format_to = "Raw") # no formatting
atable(form, arthritis, format_to = "Word") # format to MS WordIf statistics other than the default ones are required, if it possible
to return others by changing the functions atable uses to create
summary statistics, tests, effect measures and formatting.
Here is an example to calculate median, MAD, mean and SD (requires
argument x and returns a named list with class statistics_'class':
new_statistics_numeric <- function(x, ...){
statistics_out <- list(Median = median(x, na.rm = TRUE),
MAD = mad(x, na.rm = TRUE),
Mean = mean(x, na.rm = TRUE),
SD = sd(x, na.rm = TRUE))
class(statistics_out) <- c("statistics_numeric", class(statistics_out))
# We will need this new class later to specify the format
return(statistics_out)
}The suitable formatting function:
new_format_statistics_numeric <- function(x, ...){
Median_MAD <- paste(round(c(x$Median, x$MAD), digits = 1), collapse = "; ")
Mean_SD <- paste(round(c(x$Mean, x$SD), digits = 1), collapse = "; ")
out <- data.frame(tag = factor(c("Median; MAD", "Mean; SD"),
levels = c("Median; MAD", "Mean; SD")),
# use levels to retain the order of the rows
value = c(Median_MAD, Mean_SD),
stringsAsFactors = FALSE)
return(out)
}And a test function to compute both t-tests and Kolmogorov-Smirnov tests:
new_two_sample_htest_numeric <- function(value, group, ...){
d <- data.frame(value = value, group = group)
group_levels <- levels(group)
x <- subset(d, group %in% group_levels[1], select = "value", drop = TRUE)
y <- subset(d, group %in% group_levels[2], select = "value", drop = TRUE)
ks_test_out <- stats::ks.test(x, y)
t_test_out <- stats::t.test(x, y)
out <- list(p_ks = ks_test_out$p.value,
p_t = t_test_out$p.value )
return(out)
}These can then be passed to atable for use in the table:
atable(sex + age ~ trt | time, arthritis,
statistics.numeric = new_statistics_numeric,
format_statistics.statistics_numeric = new_format_statistics_numeric,
two_sample_htest.numeric = new_two_sample_htest_numeric)
## Warning in stats::ks.test(x, y): p-value will be approximate in the presence of ties
## Warning in stats::ks.test(x, y): p-value will be approximate in the presence of ties
## Warning in stats::ks.test(x, y): p-value will be approximate in the presence of ties
## Group placebo drug p stat Effect Size (CI) p_ks p_t
## 1 Month 1
## 2 Observations
## 3 149 153
## 4 sex
## 5 female 29% (43) 26% (40) 0.69 0.16 1.1 (0.67; 2)
## 6 male 71% (106) 74% (113)
## 7 missing 0% (0) 0% (0)
## 8 age
## 9 Median; MAD 55; 10.4 53; 10.4 0.55 0.61
## 10 Mean; SD 50.7; 11.2 50.1; 11
## 11 Month 3
## 12 Observations
## 13 149 153
## 14 sex
## 15 female 29% (43) 26% (40) 0.69 0.16 1.1 (0.67; 2)
## 16 male 71% (106) 74% (113)
## 17 missing 0% (0) 0% (0)
## 18 age
## 19 Median; MAD 55; 10.4 53; 10.4 0.55 0.61
## 20 Mean; SD 50.7; 11.2 50.1; 11
## 21 Month 5
## 22 Observations
## 23 149 153
## 24 sex
## 25 female 29% (43) 26% (40) 0.69 0.16 1.1 (0.67; 2)
## 26 male 71% (106) 74% (113)
## 27 missing 0% (0) 0% (0)
## 28 age
## 29 Median; MAD 55; 10.4 53; 10.4 0.55 0.61
## 30 Mean; SD 50.7; 11.2 50.1; 11(See Ströbel (2019) for passing methods via atable_options and
changing atable’s namespace)
atable only has methods for numeric, factor and ordered variables but
it possible to extend atables functionality by defining methods for
other classes (e.g. Date or surv).
Here is an example for surv objects, while vignette("atable_usage", package = "atable") contains an example with Dates.
Define the statistics and testing functions:
statistics.Surv <- function(x, ...){
survfit_object <- survival::survfit(x ~ 1)
# copy from survival:::print.survfit:
out <- survival:::survmean(survfit_object, rmean = "common")
return(list(mean_survival_time = out$matrix["*rmean"],
SE = out$matrix["*se(rmean)"]))
}
two_sample_htest.Surv <- function(value, group, ...){
survdiff_result <- survival::survdiff(value~group, rho=0)
# copy from survival:::print.survdiff:
etmp <- survdiff_result$exp
df <- (sum(1 * (etmp > 0))) - 1
p <- 1 - stats::pchisq(survdiff_result$chisq, df)
return(list(p = p,stat = survdiff_result$chisq))
}The ovarian dataset in the survival package has a suitable example…
library(survival)
## Warning: package 'survival' was built under R version 3.4.4
# set classes
ovarian <- within(survival::ovarian,
{time_to_event = survival::Surv(futime, fustat)})
# create the table
atable(ovarian, target_cols = c("time_to_event"), group_col = "rx")
## Group 1 2 p stat
## 1 Observations
## 2 13 13
## 3 time to event
## 4 mean_survival_time 650 889 0.3 1.1
## 5 SE 120 115It is also possible to have different statistics for different variables
of the same class, albeit with a little work. The approach is similar to
that used for surv objects above, but also involves defining a subset
function (most existing classes already have one, your new one probably
doesn’t).
First we create a new variable by copying the age variable and add some noise:
arthritis$noisy_age <- arthritis$age + rnorm(nrow(arthritis), 2)
class(arthritis$noisy_age) <- c("numeric2", class(arthritis$noisy_age))Now we need to define the appropriate functions…
# statistics function
statistics.numeric2 <- function(x, ...){
statistics_out <- list(Median = median(as.numeric(x), na.rm = TRUE),
MAD = mad(as.numeric(x), na.rm = TRUE),
Mean = mean(as.numeric(x), na.rm = TRUE),
SD = sd(as.numeric(x), na.rm = TRUE))
class(statistics_out) <- c("statistics_numeric2", class(statistics_out))
# We will need this new class later to specify the format
return(statistics_out)
}
# testing function
two_sample_htest.numeric2 <- function(value, group, ...){
d <- data.frame(value = as.numeric(value), group = group)
group_levels <- levels(group)
x <- subset(d, group %in% group_levels[1], select = "value", drop = TRUE)
y <- subset(d, group %in% group_levels[2], select = "value", drop = TRUE)
ks_test_out <- stats::ks.test(x, y)
t_test_out <- stats::t.test(x, y)
out <- list(p_ks = ks_test_out$p.value,
p_t = t_test_out$p.value )
return(out)
}
# subsetting function
'[.numeric2' <- function(x, i, j, ...){
y <- unclass(x)[i, ...]
class(y) <- c("numeric2", class(y))
y
}
atable(age + noisy_age ~ trt, arthritis)
## Warning in stats::ks.test(x, y, alternative = c("two.sided"), ...): p-value will be approximate in
## the presence of ties
## Group placebo drug p stat Effect Size (CI) p_ks p_t
## 1 Observations
## 2 447 459
## 3 age
## 4 Mean (SD) 51 (11) 50 (11) 0.043 0.092 0.058 (-0.072; 0.19)
## 5 valid (missing) 447 (0) 459 (0)
## 6 noisy age
## 7 Median 57 55 0.011 0.36
## 8 MAD 10 12
## 9 Mean 53 52
## 10 SD 11 11Moher, D., S. Hopewell, K. F Schulz, V. Montori, P. C Gotzsche, P J Devereaux, D. Elbourne, M. Egger, and D. G Altman. 2010. “CONSORT 2010 Explanation and Elaboration: Updated Guidelines for Reporting Parallel Group Randomised Trials.” BMJ 340 (mar23 1): c869–c869. https://doi.org/10.1136/bmj.c869.
Ströbel, Armin. 2019. “atable: Create Tables for Clinical Trial Reports.” The R Journal 11 (1): 137–48. https://journal.r-project.org/archive/2019/RJ-2019-001/RJ-2019-001.pdf.