> ## Documentation Index
> Fetch the complete documentation index at: https://docs.trainy.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Histograms

> Log and view distribution data as histograms in Pluto

## Logging

Histogram logging lets you track how distributions of values (such as weight distributions, activation values, or gradient norms) change over training steps.

To log a histogram, instantiate the `pluto.Histogram` class and pass it to `pluto.log`:

```python theme={null}
histogram = pluto.Histogram(
    data=values,
    bins=64,
)
pluto.log({"layers/layer_0/weights": histogram}, step=epoch)
```

| **Parameter** | **Type**                                | **Description**                                   |
| ------------- | --------------------------------------- | ------------------------------------------------- |
| `data`        | `Union[list, np.ndarray, torch.Tensor]` | The values to build the histogram from.           |
| `bins`        | `int`                                   | Number of bins for the histogram. Defaults to 64. |

### Examples

#### Logging Weight Distributions

```python theme={null}
import pluto
import torch

run = pluto.init(project="my-project")

model = MyModel()
for epoch in range(num_epochs):
    # ... training step ...

    # Log weight distributions for each layer
    for name, param in model.named_parameters():
        if "weight" in name:
            pluto.log({f"histograms/{name}": pluto.Histogram(param.data.cpu())}, step=epoch)
```

#### Logging Gradient Distributions

```python theme={null}
for name, param in model.named_parameters():
    if param.grad is not None:
        pluto.log({
            f"gradients/{name}": pluto.Histogram(param.grad.data.cpu(), bins=32)
        }, step=epoch)
```

## Viewing

Histograms appear as cards alongside your other metrics. Each histogram widget displays the distribution at a given training step.

<img src="https://mintcdn.com/trainy/110C0XtRepKYeipL/images/pluto/histogram-view.png?fit=max&auto=format&n=110C0XtRepKYeipL&q=85&s=0d605bfcb035fbfc56237e82d8a2b147" alt="Histogram view in the dashboard" width="1666" height="806" data-path="images/pluto/histogram-view.png" />

### Step Navigation

Use the step slider below the histogram to browse distributions at different training steps. When multiple histogram groups are displayed in the same section, their step sliders can be **linked** so that changing the step on one group changes all of them simultaneously. Click the **lock icon** on the step navigator to toggle sync on or off.

### Fullscreen View

Click the **expand** button on any histogram card's toolbar to open it in fullscreen. The fullscreen view displays the full multi-run comparison at viewport size. Use arrow keys to navigate between steps.