Data Science & Statistics: Matrix operations in R

Key Takeaways

okay we covered matrix arithmetic which means the time has come to talk about some more data science oriented operations cool I'm almost certain that if you have our studio open as you're going through the lessons you will a grasp everything a lot better but that's a given and B have the matrix dot map data we created in the previous lesson loaded if you have started a new session and don't have the script from last time saved I have entered the code we used as comments so feel free to recreate the matrix because that's what we'll be using in this lesson all right so I have my matrix of US and worldwide box-office crossings for the Matrix movie franchise and I want to learn how much in total all three movies made at the box office both around the world and in the US only luckily there is the simplest command in our that lets me do that it's called cold sums and it returns the sum for each column in your data structure the only argument you need to pass is your data like this there these are the sums of all values in each of the two columns notice that the S for sums is capitalized remember that our is case-sensitive language if you don't use the proper capitalization x' or won't know what you want it to do right as you can probably guess if there is a called sums there will probably also be a row sums function just as it was with the call names and borough names and our bind and c bind and there is let's try it out even though it isn't too useful in our particular situation because one of our columns contains the worldwide box office figures and the other contains the US cross which is part of the worldwide statistic nonetheless now we have the total u.s. and worldwide grosses for each movie in the trilogy fantastic what if I wanted to know how much on average the movies made in the US and across the globe well I can use the coal means function it works exactly like columns but gives us the means for the columns in our data structure like this again be mindful of the capital M because R is case-sensitive awesome we can also do raw means and that will give us the averages for each row in the matrix and there it is we can now find out the sums and the means for columns in ravenna matrix that is super super useful when working with larger data and you want to get a quick feel for what it has in store for you often it will be useful to save the sums and averages you compute a separate rows and columns and add them to your data structure can you guess one way to do that I'll give you a couple of seconds of course you can save each output as a vector and then simply bind what you need displayed in the matrix with our bind and see bind let's try it out I will go back up and see if the columns and coal means results in two vectors called total and average and I will create a new matrix called matrix dot prelim with our bind and stick the two new vectors to the bottom of my data and there you have it a nice and neat little matrix that tells a number in front story excellent okay let's wrap it up here but before we go I have one final question the blue pill or the red pill you take the blue pill the story ends you wake up in your bed and believe whatever you want to believe you take the red pill you stay in our land and I will show you how deep the rabbit-hole goes for more videos like this one please subscribe