Presentation on demonstrating function "within" in R

Ashu Guru Author

03/13/2019 Added

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Presentation on demonstrating function "within" in R , by Ashu Guru, University of Nebraska Raikes School (4.05 mins)

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[00:00:00.640]So many times we have to add variables to the data that we have and the goal is to
[00:00:07.435]add some sort of a variables that we can use for helping us let's say group or
[00:00:13.903]identify.
[00:00:14.640]And in this case, we are adding variables mostly to make
[00:00:18.979]groups of data within this old data.
[00:00:21.800]So if we look at the example file that we have been working with,
[00:00:26.902]we know that all the entry types that are new have their entry ID which is less
[00:00:33.087]than or equal to 50 or in other words the checks have the entry ID which is greater
[00:00:39.581]than 50.
[00:00:40.200]So what we want to do is we want to add another variable to the data frame that
[00:00:46.707]reads this file and we will call it as new that will say 0 if we are reading an
[00:00:53.215]entry that is check and one if we are reading an entry that is the new entry.
[00:00:59.680]Let's see how we can do this in R So to do this in our we are going to use what
[00:01:04.981]is called as a within function or a within statement.
[00:01:08.920]And this statement allows us to iterate or loop through or walk through the
[00:01:14.051]different elements of a variable.
[00:01:16.280]In this case we have a table or a data frame.
[00:01:19.120]So the within variable will walk through each row and then with that row we can
[00:01:24.112]perform some action.
[00:01:25.360]So let's look at this here.
[00:01:28.000]Here's a within statement.
[00:01:29.200]So I'm saying within data frame or the table if my condition is that if the
[00:01:35.832]entry ID is greater than 50 then return the value 0 otherwise one.
[00:01:41.920]So this is a short form of if else statement basically saying that if this
[00:01:46.470]condition is true then return the first value otherwise the second value.
[00:01:51.120]We are now assigning whatever is returned by this if else statement to a new
[00:01:56.454]variable new which will be a column to the actual dataframe.
[00:02:00.720]So let's take a look.
[00:02:02.240]I am going to define a working directory where my file with the data is located.
[00:02:08.520]So I set the working directory with set WD command.
[00:02:12.680]This instruction tells that I'm creating a file name variable called input file.
[00:02:19.240]I read the file in a variable called input data and then I am going to run the
[00:02:26.051]structure command which tells me that this input data is a variable of type
[00:02:32.605]data frame which has 68 observations and five variables.
[00:02:37.760]So we have plot entry name block TSW and I am going to run the head command and it
[00:02:46.121]shows me the top 6 lines.
[00:02:49.560]We see that coplot, entry name block and TSW has the
[00:02:53.739]following values.
[00:02:55.920]The next three lines that I have are the within instruction which will go and add
[00:03:04.022]a value of 0 when R finds the corresponding column.
[00:03:09.160]Value for the entry is greater than 50 and value one when the corresponding
[00:03:17.423]value is less than or equal to 50.
[00:03:21.360]Let's run these instructions and now when I look at the structure,
[00:03:25.922]it shows that there's a new column in our data frame.
[00:03:31.320]And I'm going to run a head command and it shows me that wherever R found that
[00:03:37.685]the entry was less than 50, it made the variable value as one,
[00:03:42.761]and if it was greater than 50, it made the variable value as zero.
[00:03:48.400]Now we can use this new column for grouping everything that is a new entry
[00:04:00.250]and ones that are checks.

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Presentation on demonstrating function "within" in R

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