Prepare data with advanced transformations

Note

You can only use advanced transformations for models built on tabular datasets. Multi-category text prediction models are also excluded.

Your machine learning dataset might require data preparation before you build your model. You might want to clean your data due to various issues, which might include missing values or outliers, and perform feature engineering to improve the accuracy of your model. Amazon SageMaker Canvas provides ML data transforms with which you can clean, transform, and prepare your data for model building. You can use these transforms on your datasets without any code. SageMaker Canvas adds the transforms you use to the Model recipe, which is a record of the data preparation done on your data before building the model. Any data transforms you use only modify the input data for model building and do not modify your original data source.

The following transforms are available in SageMaker Canvas for you to prepare your data for building.

Note

The preview of your dataset shows the first 100 rows of the dataset. If your dataset has more than 20,000 rows, Canvas takes a random sample of 20,000 rows and previews the first 100 rows from that sample. You can only search for and specify values from the previewed rows, and the filter functionality only filters the previewed rows and not the entire dataset.

Functions and operators

You can use mathematical functions and operators to explore and distribute your data. You can use the SageMaker Canvas supported functions or create your own formula with your existing data and create a new column with the result of the formula. For example, you can add the corresponding values of two columns and save the result to a new column.

You can nest statements to create more complex functions. The following are some examples of nested functions that you might use.

• To calculate BMI, you could use the function weight / (height ^ 2).

• To classify ages, you could use the function Case(age < 18, 'child', age < 65, 'adult', 'senior').

You can specify functions in the data preparation stage before you build your model. To use a function, do the following.

• In the Build tab of the SageMaker Canvas app, choose Functions to open up the Functions panel.

• In the Functions panel, you can choose a Formula to add to your Model Recipe. Each formula is applied to all of the values in the columns you specify. For formulas that accept two or more columns as arguments, use columns with matching data types; otherwise, you will get an error or null values in the new column.

• After you’ve specified a Formula, add a column name in the New Column Name field. SageMaker Canvas uses this name for the new column that is created.

• To add the function to your Model Recipe, choose Add.

SageMaker Canvas saves the result of your function to a new column using the name you specified in New Column Name. You can view or remove functions from the Model Recipe panel.

SageMaker Canvas supports the following operators for functions. You can use either the text format or the in-line format to specify your function.

Operator	Description	Supported data types	Text format	In-line format
Add	Returns the sum of the values	Numeric	Add(sales1, sales2)	sales1 + sales2
Subtract	Returns the difference between the values	Numeric	Subtract(sales1, sales2)	sales1 ‐ sales2
Multiply	Returns the product of the values	Numeric	Multiply(sales1, sales2)	sales1 * sales2
Divide	Returns the quotient of the values	Numeric	Divide(sales1, sales2)	sales1 / sales2
Mod	Returns the result of the modulo operator (the remainder after dividing the two values)	Numeric	Mod(sales1, sales2)	sales1 % sales2
Abs	Returns the absolute value of the value	Numeric	Abs(sales1)	N/A
Negate	Returns the negative of the value	Numeric	Negate(c1)	‐c1
Exp	Returns e (Euler's number) raised to the power of the value	Numeric	Exp(sales1)	N/A
Log	Returns the logarithm (base 10) of the value	Numeric	Log(sales1)	N/A
Ln	Returns the natural logarithm (base e) of the value	Numeric	Ln(sales1)	N/A
Pow	Returns the value raised to a power	Numeric	Pow(sales1, 2)	sales1 ^ 2
If	Returns a true or false label based on a condition you specify	Boolean, Numeric, Text	If(sales1>7000, 'truelabel, 'falselabel')	N/A
Or	Returns a boolean value of whether one of the specified values/conditions is true or not	Boolean	Or(fullprice, discount)	fullprice || discount
And	Returns a boolean value of whether two of the specified values/conditions are true or not	Boolean	And(sales1,sales2)	sales1 && sales2
Not	Returns a boolean value that is the opposite of the specified value/conditions	Boolean	Not(sales1)	!sales1
Case	Returns a boolean value based on conditional statements (returns c1 if cond1 is true, returns c2 if cond2 is true, else returns c3)	Boolean, Numeric, Text	Case(cond1, c1, cond2, c2, c3)	N/A
Equal	Returns a boolean value of whether two values are equal	Boolean, Numeric, Text	N/A	c1 = c2 c1 == c2
Not equal	Returns a boolean value of whether two values are not equal	Boolean, Numeric, Text	N/A	c1 != c2
Less than	Returns a boolean value of whether c1 is less than c2	Boolean, Numeric, Text	N/A	c1 < c2
Greater than	Returns a boolean value of whether c1 is greater than c2	Boolean, Numeric, Text	N/A	c1 > c2
Less than or equal	Returns a boolean value of whether c1 is less than or equal to c2	Boolean, Numeric, Text	N/A	c1 <= c2
Greater than or equal	Returns a boolean value of whether c1 is greater than or equal to c2	Boolean, Numeric, Text	N/A	c1 >= c2

SageMaker Canvas also supports aggregate operators, which can perform operations such as calculating the sum of all the values or finding the minimum value in a column. You can use aggregate operators in combination with standard operators in your functions. For example, to calculate the difference of values from the mean, you could use the function Abs(height – avg(height)). SageMaker Canvas supports the following aggregate operators.

Aggregate operator	Description	Format	Example
sum	Returns the sum of all the values in a column	sum	sum(c1)
minimum	Returns the minimum value of a column	min	min(c2)
maximum	Returns the maximum value of a column	max	max(c3)
average	Returns the average value of a column	avg	avg(c4)
std	Returns the sample standard deviation of a column	std	std(c1)
stddev	Returns the standard deviation of the values in a column	stddev	stddev(c1)
variance	Returns the unbiased variance of the values in a column	variance	variance(c1)
approx_count_distinct	Returns the approximate number of distinct items in a column	approx_count_distinct	approx_count_distinct(c1)
count	Returns the number of items in a column	count	count(c1)
first	Returns the first value of a column	first	first(c1)
last	Returns the last value of a column	last	last(c1)
stddev_pop	Returns the population standard deviation of a column	stddev_pop	stddev_pop(c1)
variance_pop	Returns the population variance of the values in a column	variance_pop	variance_pop(c1)

Datetime extraction

With the datetime extraction transform, you can extract values from a datetime column to a separate column. For example, if you have a column containing dates of purchases, you can extract the month value to a separate column and use the new column when building your model. You can also extract multiple values to separate columns with a single transform.

Your datetime column must use a supported timestamp format. For a list of the formats that SageMaker Canvas supports, see Time Series Forecasts in Amazon SageMaker Canvas. If your dataset does not use one of the supported formats, update your dataset to use a supported timestamp format and re-import it to Amazon SageMaker Canvas before building your model.

To perform a datetime extraction, do the following.

1. In the Build tab of the SageMaker Canvas application, choose Extract.

2. Choose the Column from which you want to extract values.

3. For Value, select one or more values to extract from the column. The values you can extract from a timestamp column are Year, Month, Day, Hour, Week of year, Day of year, and Quarter.

4. Choose Add to add the transform to the Model recipe.

SageMaker Canvas creates a new column in the dataset for each of the values you extract. Except for Year values, SageMaker Canvas uses a 0-based encoding for the extracted values. For example, if you extract the Month value, January is extracted as 0, and February is extracted as 1.

You can see the transform listed in the Model recipe section. If you remove the transform from the Model recipe section, the new columns are removed from the dataset.

Drop columns

You can exclude a column from your model build by dropping it in the Build tab of the SageMaker Canvas application. Deselect the column you want to drop, and it isn't included when building the model.

Note

If you drop columns and then make batch predictions with your model, SageMaker Canvas adds the dropped columns back to the .csv file available for you to download. However, SageMaker Canvas does not add the dropped columns back for time series models.

Rename columns

With the rename columns transform, you can rename columns in your data. When you rename a column, SageMaker Canvas changes the column name in the model input.

You can rename a column in your dataset by double-clicking on the column name in the Build tab of the SageMaker Canvas application and entering a new name. Pressing the Enter key submits the change, and clicking anywhere outside the input cancels the change. You can also rename a column by clicking the More options icon ( ), located at the end of the row in list view or at the end of the header cell in grid view, and choosing Rename.

Your column name can’t be longer than 32 characters or have double underscores (__), and you can’t rename a column to the same name as another column. You also can’t rename a dropped column.

The following screenshot shows how to rename a column by double-clicking the column name.

When you rename a column, SageMaker Canvas adds the transform in the Model recipe section. If you remove the transform from the Model recipe section, the column reverts to its original name.

Remove rows

This transform removes rows of data from the dataset where values in a specific column meet conditions that you specify. You can remove rows that have missing values, contain outliers, or meet custom conditions in a column you choose. These rows are not used when building your model.

Remove rows by missing values

Missing values are a common occurrence in machine learning datasets and can impact model accuracy. Use this transform if you want to drop rows with null or empty values in certain columns.

To remove rows that contain missing values in a specified column, do the following.

1. In the Build tab of the SageMaker Canvas application, choose Remove rows by.

2. Choose the Column you want to check for missing values.

3. For the Operation, choose Is missing.

4. Choose Add to add the transform to the Model recipe.

SageMaker Canvas drops rows that contain missing values in the Column you selected. After removing the rows from the dataset, SageMaker Canvas adds the transform in the Model recipe section. If you remove the transform from the Model recipe section, the rows return to your dataset.

Remove rows by outliers

Outliers, or rare values in the distribution and range of your data, can negatively impact model accuracy and lead to longer building times. With SageMaker Canvas, you can detect and remove rows that contain outliers in numeric columns. You can choose to define outliers with either standard deviations or a custom range.

To remove outliers from your data, do the following.

1. In the Build tab of the SageMaker Canvas application, choose Remove rows by.

2. Choose the Column you want to check for outliers.

3. For the Operation, choose Is outlier.

4. Set the Outlier range to either Standard deviation or Custom range.

5. If you choose Standard deviation, specify a SD (standard deviation) value from 1–3. If you choose Custom range, select either Percentile or Number, and then specify the Min and Max values.

6. Choose Add to add the transform to the Model recipe.

The Standard deviation option detects and removes outliers in numeric columns using the mean and standard deviation. You specify the number of standard deviations a value must vary from the mean to be considered an outlier. For example, if you specify 3 for SD, a value must fall more than 3 standard deviations from the mean to be considered an outlier.

The Custom range option detects and removes outliers in numeric columns using minimum and maximum values. Use this method if you know your threshold values that delimit outliers. You can set the Type of the range to either Percentile or Number. If you choose Percentile, the Min and Max values should be the minimum and maximum of the percentile range (0–100) that you want to allow. If you choose Number, the Min and Max values should be the minimum and maximum numeric values that you want to allow in the data.

After removing the rows from the dataset, SageMaker Canvas adds the transform in the Model recipe section. If you remove the transform from the Model recipe section, the rows return to your dataset.

Remove rows by custom values

You can remove rows with values that meet custom conditions. For example, you might want to exclude all of the rows with a price value greater than 100 when building your model. With this transform, you can create a rule that removes all rows that exceed the threshold you set.

To use the custom remove transform, do the following.

1. In the Build tab of the SageMaker Canvas application, choose Remove rows by.

2. Choose the Column you want to check.

3. Select the type of Operation you want to use, and then specify the values for the selected condition.

4. Choose Add to add the transform to the Model recipe.

For the Operation, you can choose one of the following options. Note that the available operations depend on the data type of the column you choose. For example, you cannot create a is greater than operation for a column containing text values.

Operation	Supported column type	Function
Is equal to	Binary, numeric, text, categorical	Removes rows where the value in Column equals the values you specify.
Is not equal to	Binary, numeric, text, categorical	Removes rows where the value in Column doesn't equal the values you specify.
Is less than	Numeric	Removes rows where the value in Column is less than the value you specify.
Is less than or equal to	Numeric	Removes rows where the value in Column is less than or equal to the value you specify.
Is greater than	Numeric	Removes rows where the value in Column is greater than the value you specify.
Is greater than or equal to	Numeric	Removes rows where the value in Column is greater than or equal to the value you specify.
Is between	Numeric	Removes rows where the value in Column is between or equal to two values you specify.
Contains	Text, categorical	Removes rows where the value in Column contains a values you specify.
Starts with	Text, categorical	Removes rows where the value in Column begins with a value you specify.
Ends with	Text, categorical	Removes rows where the value in Column ends with a value you specify.

After removing the rows from the dataset, SageMaker Canvas adds the transform in the Model recipe section. If you remove the transform from the Model recipe section, the rows return to your dataset.

Replace values

This transform replaces values in your dataset where the values in a specific column meet conditions that you specify. You can replace missing values or outliers. SageMaker Canvas uses the replaced values when building your model but doesn’t change your original dataset. Note that if you've dropped a column from your dataset using the Drop columns transform, you can't replace values in that column.

Replace missing values

Missing values are a common occurrence in machine learning datasets and can impact model accuracy. You can choose to drop rows that have missing values, but your model is more accurate if you choose to replace the missing values instead. With this transform, you can replace missing values in numeric columns with the mean or median of the data in a column, or you can also specify a custom value with which to replace missing values. For non-numeric columns, you can replace missing values with the mode (most common value) of the column or a custom value.

Use this transform if you want to replace the null or empty values in certain columns. To replace missing values in a specified column, do the following.

1. In the Build tab of the SageMaker Canvas application, choose Replace.

2. Choose the Column in which you want to replace missing values.

3. For Values to replace, choose Is missing.

4. Set Mode to either Automatic (default) or Manual. If you choose Automatic (default), SageMaker Canvas replaces missing values with imputed values that best fit your data. If you choose Manual, then specify the Replace with value in the next step.

5. (Optional) If you choose the Manual replacement option, set the Replace with value:

   • If your column is numeric, then select Mean, Median, or Custom. Mean replaces missing values with the mean for the column, and Median replaces missing values with the median for the column. If you choose Custom, then you must specify a custom value that you want to use to replace missing values.

   • If your column is non-numeric, then select Mode or Custom. Mode replaces missing values with the mode, or the most common value, for the column. For Custom, specify a custom value. that you want to use to replace missing values.

6. Choose Add to add the transform to the Model recipe.

After replacing the missing values in the dataset, SageMaker Canvas adds the transform in the Model recipe section. If you remove the transform from the Model recipe section, the missing values return to the dataset.

Replace outliers

Outliers, or rare values in the distribution and range of your data, can negatively impact model accuracy and lead to longer building times. SageMaker Canvas enables you to detect outliers in numeric columns and replace the outliers with values that lie within an accepted range in your data. You can choose to define outliers with either standard deviations or a custom range, and you can replace outliers with the minimum and maximum values in the accepted range.

To replace outliers in your data, do the following.

1. In the Build tab of the SageMaker Canvas application, choose Replace.

2. Choose the Column in which you want to replace outliers.

3. For Values to replace, choose Is outlier.

4. For Define outliers, choose either Standard deviation or Custom Range.

5. If you choose Standard deviation, specify a SD (standard deviation) value from 1–3. If you choose Custom Range, select either Percentile or Number, and then specify the Min and Max values.

6. For Replace with, select Min/max range.

7. Choose Add to add the transform to the Model recipe.

The Standard deviation option detects outliers in numeric columns using the mean and standard deviation. You specify the number of standard deviations a value must vary from the mean to be considered an outlier. For example, if you specify 3 for SD, a value must fall more than 3 standard deviations from the mean to be considered an outlier. SageMaker Canvas replaces outliers with the minimum value or maximum value in the accepted range. For example, if you configure the standard deviations to only include values from 200–300, then SageMaker Canvas changes a value of 198 to 200 (the minimum).

The Custom Range option detects outliers in numeric columns using minimum and maximum values. Use this method if you know your threshold values that delimit outliers. You can set the Type of the custom range to either Percentile or Number. If you choose Percentile, the Min and Max values should be the minimum and maximum of the percentile range (0–100) that you want to allow. If you choose Number, the Min and Max values should be the minimum and maximum numeric values that you want to allow. SageMaker Canvas replaces any values that fall outside of the minimum and maximum to the minimum and maximum values. For example, if your range only allows values from 1–100, then SageMaker Canvas changes a value of 102 to 100 (the maximum).

After replacing the values in the dataset, SageMaker Canvas adds the transform in the Model recipe section. If you remove the transform from the Model recipe section, the original values return to the dataset.

Filter rows

The filter functionality filters the previewed rows (the first 100 rows of your dataset) according to conditions that you specify. Filtering rows creates a temporary preview of the data and does not impact the model building. You can filter to preview rows that have missing values, contain outliers, or meet custom conditions in a column you choose.

Filter rows by missing values

Missing values are a common occurrence in machine learning datasets. If you have rows with null or empty values in certain columns, you might want to filter for and preview those rows.

To filter missing values from your previewed data, do the following.

1. In the Build tab of the SageMaker Canvas application, choose Filter by rows ( ).

2. Choose the Column you want to check for missing values.

3. For the Operation, choose Is missing.

SageMaker Canvas filters for rows that contain missing values in the Column you selected and provides a preview of the filtered rows.

Filter rows by outliers

Outliers, or rare values in the distribution and range of your data, can negatively impact model accuracy and lead to longer building times. SageMaker Canvas enables you to detect and filter rows that contain outliers in numeric columns. You can choose to define outliers with either standard deviations or a custom range.

To filter for outliers in your data, do the following.

1. In the Build tab of the SageMaker Canvas application, choose Filter by rows ( ).

2. Choose the Column you want to check for outliers.

3. For the Operation, choose Is outlier.

4. Set the Outlier range to either Standard deviation or Custom range.

5. If you choose Standard deviation, specify a SD (standard deviation) value from 1–3. If you choose Custom range, select either Percentile or Number, and then specify the Min and Max values.

The Standard deviation option detects and filters for outliers in numeric columns using the mean and standard deviation. You specify the number of standard deviations a value must vary from the mean to be considered an outlier. For example, if you specify 3 for SD, a value must fall more than 3 standard deviations from the mean to be considered an outlier.

The Custom range option detects and filters for outliers in numeric columns using minimum and maximum values. Use this method if you know your threshold values that delimit outliers. You can set the Type of the range to either Percentile or Number. If you choose Percentile, the Min and Max values should be the minimum and maximum of the percentile range (0-100) that you want to allow. If you choose Number, the Min and Max values should be the minimum and maximum numeric values that you want to filter in the data.

Filter rows by custom values

You can filter for rows with values that meet custom conditions. For example, you might want to preview rows that have a price value greater than 100 before removing them. With this functionality, you can filter rows that exceed the threshold you set and preview the filtered data.

To use the custom filter functionality, do the following.

1. In the Build tab of the SageMaker Canvas application, choose Filter by rows ( ).

2. Choose the Column you want to check.

3. Select the type of Operation you want to use, and then specify the values for the selected condition.

For the Operation, you can choose one of the following options. Note that the available operations depend on the data type of the column you choose. For example, you cannot create a is greater than operation for a column containing text values.

Operation	Supported column type	Function
Is equal to	Binary, numeric, text, categorical	Filters rows where the value in Column equals the values you specify.
Is not equal to	Binary, numeric, text, categorical	Filters rows where the value in Column doesn't equal the values you specify.
Is less than	Numeric	Filters rows where the value in Column is less than the value you specify.
Is less than or equal to	Numeric	Filters rows where the value in Column is less than or equal to the value you specify.
Is greater than	Numeric	Filters rows where the value in Column is greater than the value you specify.
Is greater than or equal to	Numeric	Filters rows where the value in Column is greater than or equal to the value you specify.
Is between	Numeric	Filters rows where the value in Column is between or equal to two values you specify.
Contains	Text, categorical	Filters rows where the value in Column contains a values you specify.
Starts with	Text, categorical	Filters rows where the value in Column begins with a value you specify.
Ends with	Text, categorical	Filters rows where the value in Column ends with a value you specify.

After you set the filter operation, SageMaker Canvas updates the preview of the dataset to show you the filtered data.