# Candle z-score (`ta.cdl_z`)



<a id="ta-cdl-z"></a>

Standardize open, high, low, and close separately to measure each price's deviation from its rolling mean.

[Indicator catalog](https://docs.openbacktesting.com/reference/indicators/index.md) · [How to use indicators](https://docs.openbacktesting.com/reference/indicator-api/index.md)

## Run this example

This complete script uses bundled data. It observes the selected output without placing trades.

```python
import numpy as np
from openbacktesting import Backtest, Strategy
from openbacktesting.test import GOOG

data = GOOG.copy()

class Example(Strategy):
    def init(self):
        self.value = self.ta.cdl_z()
        self.latest_value = None

    def next(self):
        channel = self.value.open
        if channel.valid[-1]:
            self.latest_value = float(channel[-1])

result = Backtest(data, Example).run()
print(result["_strategy"].latest_value)
```

## Call and parameters

```python
self.ta.cdl_z(*, length=30, ddof=1, inputs=None, backend=None, required_outputs=None)
```

Register in `init()`. Read the returned channel in `next()` after checking `valid[-1]`.

| Parameter | Meaning | Type | Default | Allowed values |
| --- | --- | --- | --- | --- |
| `length` | Calculation window in observations. | `int` | `30` | Minimum: `2` |
| `ddof` | Degrees of freedom subtracted from the variance denominator. | `int` | `1` | Minimum: `0` |

`source`/named source arguments accept a column name or same-run single-channel handle. Alternatively, `inputs` maps each input below to a column or handle. `backend` selects a supported implementation; `required_outputs` selects channels for readiness diagnostics. See [shared arguments and handles](https://docs.openbacktesting.com/reference/indicator-api/index.md#bind-inputs-and-read-outputs).

## Inputs and outputs

Required inputs: `open_`, `high`, `low`, `close`.

| Channel | Meaning |
| --- | --- |
| `open` | Open output |
| `high` | High output |
| `low` | Low output |
| `close` | Close output |

## Reading values safely

Insufficient history or missing inputs can make a channel invalid. Check that channel's `valid` mask; `ready` is diagnostic and never suppresses `next()`. Multi-output results may have different valid channels on the same bar.

Zero can be a valid non-triggered pattern; validity is separate from its score. A score is not an order or a guaranteed direction signal.

[Indicator catalog](https://docs.openbacktesting.com/reference/indicators/index.md) · [Custom calculations](https://docs.openbacktesting.com/reference/strategy/index.md#register-custom-calculations)