R Tutorial : Intermediate Functional Programming with purrr

Key Takeaways

hello and welcome to this course on programming whisper I'm kunafa I'm a data scientist in our ARCA as you can only Amy there is a picture of me drinking coffee a big part of my day job is writing our code and I use / to help me optimize my workflow notably I use / for writing functions which is what you'll do in this course before starting this course make sure you've got some basic knowledge of iteration using / if you're not familiar with it there are some great resources that can help you learn about iteration with / if you're already familiar iterating with / you can start with schools right now almost every iteration process has two sides the first other elements we iterate over a second is we function we apply to each element / follows with format the first per function everyone learns is the map function map as two elements first dot X which is the object we are iterating over its object can either be a vector a list or a data frame a second part includes that F and V dot argument which represents the functional part of the iteration it's a description of what happens to each element of the object in this course you'll learn how to deal with the second half of a basic / skeleton the dot F and V dot arguments for this course I have extracted three lists from a dataset taken from the open data portal of a French city of Samara this dataset gathers account of a number of visits on the website some are up my fare each shop is newly created lists is a year 2014 2015 and 2016 it contains 12 sub lists corresponding to month each month is a vector with a number of website visits per day these list objects are an extraction of a full data set this list format is one you regularly encounter when carrying data on the web notably when you have to do with a JSON format which is passed as a nested list in our let's start with a refresher of per basic functions using these three lists first let's see the map function the map function runs without f function on each element of dot X and always return the list here we are mapping with some function on the list visit underscore 2015 when strength of Perl is with this types table this means that you always know up front the class of the output here for example we are using map and discord dbl map underscore GPL does the same operation as map but the output is different as you can see the result is a numeric vector rather than a list let's now imagine we want to add visits from 2015 and 2016 to do this I can use the map to function to get a list and its counterpart map to underscore TBL to get a vector of numeric what if we want to do the same computation as we won from the previous slide but with free lists in per there is no map free map for etc if you want to map over move on to elements you need to pass a list of elements to the P map function to iterate over elements in three or more lists you'll need to put all these lists in a novelist and pathways master list as the first argument of P map now it's your turn to refresh your memory