Presentation describing the aggregate function in R

Ashu Guru Author

03/13/2019 Added

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Presentation describing the aggregate function in R , by Ashu Guru, Univ of Nebraska Raikes School (4 mins)

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[00:00:00.840]We now take a look at a function in R which is called as aggregate.
[00:00:07.560]Suppose that we have data in a table form.
[00:00:11.800]So suppose that you have data which is multiple columns.
[00:00:16.600]In this case we have group on attribute 1 and attribute 2 and then we have a set of
[00:00:22.602]rows for that data.
[00:00:24.520]Further suppose that the data is stored in a CSV file.
[00:00:27.960]So just to make our example simpler, I have it in a CSV file.
[00:00:33.040]I'll show it to you here.
[00:00:35.320]So here is my aggregate CSV dot TXT and I'll open it with a text editor and here
[00:00:43.370]is that same data.
[00:00:47.280]So I have 120, 20, 120, 20 and the last one is 101, 25, 18. 101,
[00:00:53.418]25, 18.
[00:00:56.200]So what we want is that we want to aggregate the rows in column attribute 1.
[00:01:02.560]So we want to aggregate these rows based upon the common value in column group on
[00:01:09.306]South.
[00:01:09.800]We want to somehow aggregate them based on the column groupOns same value.
[00:01:15.920]So in this case, we want to aggregate these 4 rows and
[00:01:20.375]these two rows together.
[00:01:22.320]So these two rows will have one row output,
[00:01:24.938]these 4 rows will have one row output.
[00:01:28.600]And the aggregate output must be the average value of the attribute 1.
[00:01:33.680]So in this case, we want that the aggregated value should
[00:01:37.652]be the average.
[00:01:38.680]It could be the sum let's say.
[00:01:40.520]But here we want to do an average value of it.
[00:01:43.840]So in this case for 100 we have 20, 30, 35,
[00:01:48.172]35 that's about 70 hundred and twenty so 120 divided by....
[00:01:54.080]Since there are 1, 2, 3, 4 rows by 4 is 30 so we want the output
[00:02:00.229]to be 3400 and for 101 it is 25 + 15 which is 40.
[00:02:04.960]So the output should be 40 / 2 which is 20.
[00:02:09.400]In order to perform this, we can use an R function which is called
[00:02:13.353]as aggregate.
[00:02:14.680]First setting my working directory to the folder where my CSV file aggregate CSV
[00:02:20.718]TXT is.
[00:02:21.240]Now I am loading the CSV file since it has a header,
[00:02:25.327]header is true and it is a comma separated.
[00:02:29.120]I'm loading into a variable called tab data.
[00:02:32.040]I run that.
[00:02:33.680]Now let me print column Groupon of the tab data.
[00:02:38.760]So here it is.
[00:02:41.000]So we see that the Groupon column has 100, 100, 101 and 101 as we had expected. 1, 2,
[00:02:48.985]3, 4 hundreds, 2, 3, 4 hundreds and then 101 and 101.
[00:02:54.280]And now I am going to apply the aggregate function on the list attributes.
[00:03:02.720]So in this case in order to get the list reference I will say tab data and then in
[00:03:08.957]square brackets attribute 1 and then I have to pass a list to the second
[00:03:14.443]argument.
[00:03:15.280]And in this case indexing should be based upon Groupon column of my tab data.
[00:03:24.200]And then I want that the output is mean.
[00:03:28.280]So once I do that I can print what is the value of aggregated mean.
[00:03:34.000]My aggregated mean has a column My Grouped index value which has 100 and 101
[00:03:40.431]and then it has the mean value based upon the common value in the column GroupOn.

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Presentation describing the aggregate function in R

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