Transform Numbers

Arithmetic

❯make a new table that takes the orders table and adds 10 to the price column

⏺

Needs a transformer. Getting its guide.

Called tabsdata 2 times (ctrl+o to expand)

⏺

Generating — the + operator works directly on a column expression, so no method call is needed. add() is the method form and does the same thing.

Called tabsdata 3 times (ctrl+o to expand)

⏺

The transformer, registered in subscriptions:

@transformer(
  input_tables=["orders"],
  output_tables=["orders_bumped"],
)
def bump_price(orders: TableFrameSpec) -> TableFrameSpec:
  expr = col("price") + 10
  return orders.with_columns(expr)

⏺

Execution committed, 0 failures.

⏺

subscriptions/orders_bumped is live — 10 added to every price:

┌───────┐
│ price │
├───────┤
│ 110   │
├───────┤
│ 50    │
└───────┘

Transformed tables

orders

price
100
40

2 rows

orders_bumped

price
110
50

2 rows

Round and clip

❯make a new table that takes the items table and rounds the price column to 2 decimal places

⏺

Needs a transformer. Getting its guide.

Called tabsdata 2 times (ctrl+o to expand)

⏺

Generating — round(2) rounds to that many decimal places.

Called tabsdata 3 times (ctrl+o to expand)

⏺

The transformer, registered in subscriptions:

@transformer(
  input_tables=["items"],
  output_tables=["items_rounded"],
)
def round_price(items: TableFrameSpec) -> TableFrameSpec:
  expr = col("price").round(2)  # Round to 2 decimal places
  return items.with_columns(expr)

⏺

Execution committed, 0 failures.

⏺

subscriptions/items_rounded is live — price to 2 decimal places:

┌────────┬───────┐
│  item  │ price │
├────────┼───────┤
│ widget │ 19.99 │
├────────┼───────┤
│ gadget │ 4.2   │
└────────┴───────┘

Transformed tables

items

item	price
widget	19.9876
gadget	4.201

2 rows

items_rounded

item	price
widget	19.99
gadget	4.2

2 rows

Powers, roots and logs

❯make a new table that takes the readings table and takes the absolute value of the change column

⏺

Needs a transformer. Getting its guide.

Called tabsdata 2 times (ctrl+o to expand)

⏺

Generating — abs() drops the sign.

Called tabsdata 3 times (ctrl+o to expand)

⏺

The transformer, registered in subscriptions:

@transformer(
  input_tables=["readings"],
  output_tables=["readings_absolute"],
)
def abs_change(readings: TableFrameSpec) -> TableFrameSpec:
  expr = col("change").abs()
  return readings.with_columns(expr)

⏺

Execution committed, 0 failures.

⏺

subscriptions/readings_absolute is live — the sign dropped:

┌────────┐
│ change │
├────────┤
│ 4.5    │
├────────┤
│ 2      │
└────────┘

Transformed tables

readings

change
-4.5
2

2 rows

readings_absolute

change
4.5
2

2 rows

Trigonometry

❯make a new table that takes the readings table and takes the sine of the angle column

⏺

Needs a transformer. Getting its guide.

Called tabsdata 2 times (ctrl+o to expand)

⏺

Generating — sin(). The input is read in radians, so use radians() first if the column holds degrees.

Called tabsdata 3 times (ctrl+o to expand)

⏺

The transformer, registered in subscriptions:

@transformer(
  input_tables=["readings"],
  output_tables=["readings_sine"],
)
def sin_angle(readings: TableFrameSpec) -> TableFrameSpec:
  expr = col("angle").sin()
  return readings.with_columns(expr)

⏺

Execution committed, 0 failures.

⏺

subscriptions/readings_sine is live — the sine of each angle:

┌────────┐
│ angle  │
├────────┤
│ 0      │
├────────┤
│ 0.8415 │
└────────┘

Transformed tables

readings

angle
0
1

2 rows

readings_sine

angle
0
0.8415

2 rows

Compare with earlier rows

❯make a new table that takes the readings table and takes the change in the value column from the previous row

⏺

Needs a transformer. Getting its guide.

Called tabsdata 2 times (ctrl+o to expand)

⏺

Generating — diff() compares each row with the one before it, so the first row has no predecessor and comes out null. It reads the table in its current order.

Called tabsdata 3 times (ctrl+o to expand)

⏺

The transformer, registered in subscriptions:

@transformer(
  input_tables=["readings"],
  output_tables=["readings_delta"],
)
def row_delta(readings: TableFrameSpec) -> TableFrameSpec:
  expr = col("value").diff()  # Difference from previous row
  return readings.with_columns(expr)

⏺

Execution committed, 0 failures.

⏺

subscriptions/readings_delta is live — the change from the previous row, null on the first:

┌───────┐
│ value │
├───────┤
│ null  │
├───────┤
│ 3     │
├───────┤
│ -4    │
└───────┘

Transformed tables

readings

value
10
13
9

3 rows

readings_delta

value
null
3
-4

3 rows