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Intro to Segmentation¶

Sometimes, certain subgroups of data can behave very differently from the overall dataset. When monitoring the health of a dataset, it’s often helpful to have visibility at the sub-group level to better understand how these subgroups are contributing to trends in the overall dataset. whylogs supports data segmentation for this purpose.

Data segmentation is done at the point of profiling a dataset.

Segmentation can be done by a single feature or by multiple features simultaneously. For example, you could have different profiles according to the gender of your dataset ("M" or "F"), and also for different combinations of, let's say, Gender and City Code. You can also further filter the segments for specific partitions you are interested in - let's say, Gender "M" with age above 18.

In this example, we will show you a number of ways you can segment your data, and also how you can write these profiles to different locations.

Table of Content¶

1. Segmenting on a single column
2. Segmenting on multiple columns
3. Filtering Segments
4. Writing Segmented Results to Disk
5. Sending Segmented Results to WhyLabs

Installing whylogs¶

If you don't have it installed already, install whylogs:

Getting the Data & Defining the Segments¶

Let's first download the data we'll be working with.

This dataset contains transaction information for an online grocery store, such as:

• product description
• category
• user rating
• market price
• number of items sold last week

Segmenting on a Single Column¶

It looks like the category feature is a good one to segment on. Let's see how many categories there are for the complete dataset:

There are 11 categories.

We might be interested in having access to metrics specific to each category, so let's generate segmented profiles for each category.

column_segments is a dictionary for different SegmentationPartition, with informations such as id and additional logic. For the moment, all we're interested in is that we can pass it to our DatasetSchema in order to generate segmented profiles while logging:

Since we had 11 different categories, we can expect the results to have 11 segments. Let's make sure that is the case:

Great.

Now, let's visualize the metrics for a single segment (the first one).

Results can have multiple partitions, and each partition can have multiple segments. Segments within a partition are non-overlapping. Segments across partitions, however, might overlap.

In this example, we have only one partition with 11 non-overlapping segments. Let's fetch the available segments:

Now, let's visualize the metrics for the first segment:

We can see that the first segment is for product transactions of the Baby Care category, and we have 707 rows for that particular segment.

Segmenting on More than one Column¶

We might also be interested in segmenting based on more than one segment.

Let's say we are interested in generating profiles for every combination of category and rating. That way, we can inspect the metrics for, let's say, for Beverages with rating of 5.

This time, we'll use SegmentationPartition to create the partition:

Let's create our dictionary with the only partition we have:

Again, let's check the first segment:

The first segment is now for transactions of Baby Care category with rating of 3. There are 162 records for this specific segment.

Filtering the Segments¶

You can further select data in a partition by using a SegmentFilter.

Let's say you are interested only in the Baby Care category. Instead of generating all 11 segmented features, you can specify a SegmentFilter to get only one segment.

We can do so by specifying a filter function to the filter property of the Partition:

We're passing a simple lambda function here, but you can define more complex scenarios by passing any Callable to it.

Now, we just repeat the logging process:

We can see that now we have only 1 segment.

Filtering on other columns¶

You don't need to filter on the same category you're segmenting on. In fact, you can use multiple columns to get very specific slices of interest for your data.

Unlike segmenting on multiple columns, with filtering you don't need to get the segments for the complete cartesian product of your rules. This avoids combinatorial explosions for cases when you are interested in a very specific slice of your data, and are not particularly interested in all possible group combinations.

Let's say high-quality, high-cost products are key to a certain promotion you want to release. You can create segments based on category, just as before, and can further filter it to track only data for your defined rule.

The only difference between this case and the previous one is the lambda function provided, but for reproducibility let's repeat the whole code again:

Notice that we now have a count of 389, whereas our first example had a count of 707. That's because now we're filtering the data to track only points that match our rule for high-quality, high-cost products.

Writing the Segments to Disk¶

Once you have the segmented results, you can use the results' writer method to write it to disk, for example:

This will write 11 binary profiles to the specified folder. Let's check with listdir:

Sending Segmented Profiles to WhyLabs¶

With the whylogs Writer, you can write your profiles to different locations. If you have a WhyLabs account, you can easily send your segmented profiles to be monitored in your dashboard.

We will show briefly how to do it in this example. If you want more details, please check the WhyLabs Writer Example (also available in our documentation).

Provided you already have the required information and keys, let's first set our environment variables:

Then, it's as simple as calling writer("whylabs"):

You should be able to see your segments at your dashboard at the segments tab: