Rbind() function combines vector, matrix or data frame by rows.
Logical and factor columns are converted to integers. Return the matrix obtained by converting all the variables in a data frame to numeric mode and then binding them together as the columns of a matrix. For example, if you know that your loop won’t iterate more than 10,000 times, you can initialize your vector with 10,000 elements, even if you will not use them all. Later, when the loop has finished executing, you can pick only the non-null elements. If you don’t know the number of iterations, but you have an upper bound for them, you can define the vector with this upper bound. For example, if you know your loop will iterate 10,000 times, you can initialize the vector this way: mylist <- vector("list", 10000)Īfter this, you can use a for loop and set the value of each element by its index: i <- 1 If you know beforehand how many times your loop will iterate, then instead of growing a list of elements, you can define a vector of fixed length and use it to hold all the elements. The below example does the same as the previous one, but more efficiently. With the length function, you can get the number of elements in the list and assign each new element to the index behind the last element: length(mylist) + 1. Append to a List in R With the length FunctionĪ more efficient approach to append an arbitrary number of elements to a list within a loop is to use the length function in each iteration. When working with large data sets, the time it takes to add all the elements could be tremendous. The problem with the previous example is that each time the concatenation is executed, the whole list is copied. In this example, a value ( i*3) is added to a list until the index variable reaches 10,000: i <- 1 Within each iteration, an element is added by using the c function. This tutorial will introduce the most efficient ways to append elements to a list in an R loop.Ī common way to implement such an algorithm would be to create a while loop and use the c (concatenate) command within the loop. Some of them could become sluggish when the number of elements is high. There are many ways to use a loop to add an arbitrary number of elements to a list in R. Append to a List in R With the length Function.
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