# Demo gotran

In this demo we will demonstrate how you can use the python API to visualize the dependencies
in the Hodgkin Huxley model  of the squid axon from 1952. This model is taken
from <https://models.cellml.org/workspace/hodgkin_huxley_1952> and converted to a
gotran `.ode` file using `gotran` and the `cellml2gotran` script

First we make the necessary imports

```python
import gotran
import matplotlib.pyplot as plt
import networkx as nx
from modelgraph import DependencyGraph
```

and load the ode file

```python
ode = gotran.load_ode("hodgkin_huxley_squid_axon_model_1952_original.ode")
```

Next we build the dependency graph

```python
graph = DependencyGraph(ode)
```

and get the graph of the expressions that depends on the parameter `g_Na`

```python
G_g_Na = graph.inv_dependency_graph("g_Na")
```

We plot this using `matplotlib`

```python
nx.draw(G_g_Na, with_labels=True, font_size=10, node_size=2000)
plt.savefig("g_Na_mpl.png")
```

![_](_static/g_Na_mpl.png)

and using `pydot`

```python
P_g_Na = nx.nx_pydot.to_pydot(G_g_Na)
P_g_Na.write_png("g_Na_pydot.png")
```

![_](_static/g_Na_pydot.png)

Finally we grab the graph of the dependencies of `dV_dt`

```python
# Visualize what dV_dt depdens on
G_dV_dt = graph.dependency_graph("dV_dt")
# and visualize this using `pydot`
#
```

```python
P_dV_dt = nx.nx_pydot.to_pydot(G_dV_dt)
P_dV_dt.write_png("dV_dt_pydot.png")
```

![_](_static/dV_dt_pydot.png)