Hello Everyone, I am [INAUDIBLE] Sarikov. In this video lecture we will learn how
to use concatenation operator in R. We will learn how to find 5 number
summary of a data set in R. And learn how to find sample mean and
sample standard deviation of a data set. Here I have R up and running, and
this is basically our R command shell. One thing we can do is basically clear
up the console, our console here. If I say clear out, and
then I have whole R console cleaned. Now I can start entering my commands. Let me just mention now, that in R, if you start with number sign it
means that we are commenting here. So we are commenting and
it just ignores that command. So in this lecture we're going to first
start using concatenation operator for entering data set in R. So how do we do that? Let's say I have the following data set. I have a data set, which basically contains 5 numbers, 35, 8, 10, 23, and 42. Now how can we enter this data
set to our variable in R? First, you have to define
the name of the variable. We try to be as descriptive as
possible when we define our variables. Let's see, we see data.1. So these are in data.1,
so this are data.1. And we use concatenation operator,
and it starts with C. And we have to enter our numbers
in here using comma in between. So we can say 35, 8, 10, 23, and 42. And once we do that,
then we store our data set into a data.1, data.1 variable. See, if i just write data.1,
it will show me this part numbers, in that data set and
the 1 is just index of the first guy here. Or I can just say print(data.1) and
then I will get the same data set. So this is how we use concatenation. By the way, we can use our fourth arrow key in our keyboard
to go to previous commands. So if I go back to data.1, the
concatenation operator, if I, for example, increase spaces in between these numbers,
let's see what happens. If I just go back and
look at the date, print data.1. Well, nothing has changed, so,
basically when you have spaces in between when you use concatenation,
it ignores spaces. But if I just go back and, for
example, forget about this comma here. So I have 35, 8, 10, 23, but
I have forgot the comma here. And come back, well,
then this is all unexpected numeric. There is an unexpected numeric constant. And it doesn't understand 23 or
42, so we cannot do that. So this is how we use
concatenation operator. Now that we have our data sets, we then
go back and try to fix that with comma. Okay, now that we have our data set, which is data.1,
we can do something statistics on it. For example, we can find 5
number summary of this data set. So how do we do this,
we can just say summary and so every time we put a function in r,
we have to have a parenthesis. And then argument goes into that function,
argument here is a data set for that function. If I do that and push Enter,
it gives me 5 number summary. Well, in fact it gives me 6 numbers but
it includes a mean here as well. So the usual 5 number summary
is the mean of data set, first quartile, median, third quartile and
the maximum of the data set. But here I also have the mean
of the data set, all right. But if you want to just find
a mean of this data set directly, and the command and function is the mean. And the argument again is the data.1, because we want to find sample mean of
our data set and this is what we get. Let me mention now that the definition
of the sample mean is the basically sum of these numbers in this data set
over number of points in the data set. For example,
if I just do the sum of data.1, then I will actually get
the sum of all these numbers. And if I divide that by 5, which means I
should get sample average, sample mean, which is the same number, okay. And then one last thing
I would like to mention, is the standard deviation,
actually sample standard deviation. If you watch,
you'll find sample standard deviation, we use a command sd for
standard deviation. People data.1, and
we find our standard deviation. So what have you learned in this lecture? You have learned how to enter a data set
in R using the concatenation operator. You learned how to find 5
number summary of a data set in R using a summary function. And also you have learned how to find
sample mean and sample standard deviation of a data set in R using this functions
called mean and standard deviation.