![]() According to a recent Cochrane review, current COVID-19 antibody tests are around 90% sensitive and 98% specific. Sensitivity, specificity and predictive valuesĪs with any good diagnostic test, COVID-19 antibody tests need to be highly sensitive, which means that most people who have had the disease get a positive result and highly specific, which means that most people who have not had the disease get a negative result. Fortunately, or unfortunately, it is a bit more complicated than that. Maybe you have received a positive test result and are now resting easy in the knowledge that you cannot get COVID-19 again. Maybe you are convinced that you have had COVID-19 but your antibody test result has come back negative. Some people prefer chaining to nesting because the functions applied can be read from left to right rather than from inside out.Widespread antibody testing has long been hailed as key to getting back to “normality,” by providing a way of determining who has already contracted COVID-19 and is potentially no longer at risk. Thus iris %>% head() %>% summary() is equivalent to summary(head(iris)). For example in the chain below, iris is passed to head(), then the result of that is passed to summary(). Often, %>% is called multiple times to "chain" functions together, which accomplishes the same result as nesting. Thus, iris %>% head() is equivalent to head(iris). Sepal.Length Sepal.Width Petal.Length Petal.Width Species ![]() In the following example, the data frame iris gets passed to head(): library(magrittr) What the function does is to pass the left hand side of the operator to the first argument of the right hand side of the operator. It works like a pipe, hence the reference to Magritte's famous painting The Treachery of Images. The infix operator %>% is not part of base R, but is in fact defined by the package magrittr ( CRAN) and is heavily used by dplyr ( CRAN). ![]()
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