dpdata.md

# Prepare data with dpdata

One can use the a convenient tool [`dpdata`](https://github.com/deepmodeling/dpdata) to convert data directly from the output of first principle packages to the DeePMD-kit format.

To install one can execute 
```bash
pip install dpdata
```

An example of converting data [VASP](https://www.vasp.at/) data in `OUTCAR` format to DeePMD-kit data can be found at
```
$deepmd_source_dir/examples/data_conv
```

Switch to that directory, then one can convert data by using the following python script
```python
import dpdata
dsys = dpdata.LabeledSystem('OUTCAR')
dsys.to('deepmd/npy', 'deepmd_data', set_size = dsys.get_nframes())
```

`get_nframes()` method gets the number of frames in the `OUTCAR`, and the argument `set_size` enforces that the set size is equal to the number of frames in the system, viz. only one `set` is created in the `system`. 

The data in DeePMD-kit format is stored in the folder `deepmd_data`.

A list of all [supported data format](https://github.com/deepmodeling/dpdata#load-data) and more nice features of `dpdata` can be found at the [official website](https://github.com/deepmodeling/dpdata).