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## R sweep fun

It is better suited for use inside other functions.

Every functional programming language has three tools for this: Map Reduce and Filter.

Rm false) stopifnot(length(x) length(y meric(x meric(y) vapply(seq_along(x function(i) add(xi, yi,.

In this section youll learn about three common cases: modifying in place recursive functions while loops Its possible to torture these problems to use a functional, but its not a good idea.Position returns the position of the first element that matches the predicate (or the last element if right true).In MLE, we have two sets of parameters: the data, which is fixed for a given problem, and the parameters, which vary as we try to find the maximum.Lapply makes it easier to work with lists by eliminating much of the boilerplate associated with looping.With apply the argument is absent.Combining closures with optimisation gives rise to the following approach to solving MLE problems.Our toy example, depicted in figure 2 can be coded as: the operation is shown in the left part of figure.Use sapply and an anonymous function to extract the p-value from every trial.

Next, you specify the second parameter, which is 2: our margin is column.

Rm true) # 1 0 Why did we pick an identity of 0?

It is often used with apply to standardise arrays.

The earthlink internet promotion code following example varies the amount of trimming applied when computing the mean of a fixed.The New S Language.At first glance, these functions dont seem to fit in with the theme of eliminating loops, but if you dig deeper youll find out that they are all implemented using an algorithm that involves iteration.Instead, its much better to create the space youll need for the output and then fill.Bootstraps - lapply(1:10, function(i) rows - sample(1:nrow(mtcars rep true) mtcarsrows, ) For each model in the previous two exercises, extract R 2 using the function below.Vapply is a variant of sapply that allows you to describe what the output should be, but there are no corresponding variants for tapply apply or Map.One obvious generalisation is to add more than two numbers.Just replace the loop with lapply by using -: lapply(names(trans function(var) mtcarsvar - transvar(mtcarsvar) ) The for loop is gone, but the code is longer and much harder to understand.Randomise - function(f) f(runif(1e3) randomise(mean) #.4821537 randomise(mean) #.5041088 randomise(sum) # 1 525.3343, the chances are that youve already used a functional: the three most frequently used are lapply apply and tapply.