python-control · AndrewTrepagnier · Jul 26, 2025 · Jul 26, 2025 · Jul 26, 2025 · Jul 26, 2025
diff --git a/control/__init__.py b/control/__init__.py
@@ -35,6 +35,7 @@
 specialized functionality:
 
 * :mod:`~control.flatsys`: Differentially flat systems
+* :mod:`~control.interactive`: Interactive plotting tools
 * :mod:`~control.matlab`: MATLAB compatibility module
 * :mod:`~control.optimal`: Optimization-based control
 * :mod:`~control.phaseplot`: 2D phase plane diagrams
@@ -87,6 +88,13 @@
 from .passivity import *
 from .sysnorm import *
 
+# Interactive plotting tools
+try:
+    from .interactive import *
+except ImportError:
+    # Interactive tools may not be available if plotly is not installed
+    pass
+
 # Allow access to phase_plane functions as ct.phaseplot.fcn or ct.pp.fcn
 from . import phaseplot as phaseplot
 pp = phaseplot

diff --git a/control/interactive/README.md b/control/interactive/README.md
@@ -0,0 +1,99 @@
+# Interactive Plotting Tools
+
+This module provides interactive plotting capabilities for the Python Control Systems Library.
+
+## Root Locus GUI
+
+The `root_locus_gui` function creates an interactive root locus plot with hover functionality.
+
+### Features
+
+- **Hover Information**: Hover over the root locus to see gain, damping ratio, and frequency
+- **Original Plot Style**: Uses the same visual style as the original matplotlib root locus plots
+- **Interactive Info Box**: Small info box in the corner shows real-time information
+- **Cursor Marker**: Green dot follows your mouse to show exactly where you are on the root locus
+- **Poles and Zeros**: Visual display of open-loop poles and zeros
+- **Customizable**: Various options for display and interaction
+
+### Basic Usage
+
+```python
+import control as ct
+
+# Create a system
+s = ct.tf('s')
+sys = 1 / (s**2 + 2*s + 1)
+
+# Create interactive root locus plot
+gui = ct.root_locus_gui(sys)
+gui.show()
+```
+
+### Advanced Usage
+
+```python
+# Customize the plot
+gui = ct.root_locus_gui(
+    sys,
+    title="My Root Locus",
+    show_grid_lines=True,
+    damping_lines=True,
+    frequency_lines=True
+)
+gui.show()
+```
+
+### Parameters
+
+- `sys`: LTI system (SISO only)
+- `gains`: Custom gain range (optional)
+- `xlim`, `ylim`: Axis limits (optional)
+- `grid`: Show s-plane grid (default: True)
+- `show_poles_zeros`: Show poles and zeros (default: True)
+- `show_grid_lines`: Show grid lines (default: True)
+- `damping_lines`: Show damping ratio lines (default: True)
+- `frequency_lines`: Show frequency lines (default: True)
+- `title`: Plot title
+
+### Hover Information
+
+When you hover over the root locus, you can see:
+
+- **Gain**: The current gain value
+- **Pole**: The pole location in the s-plane
+- **Damping**: Damping ratio (for complex poles)
+- **Frequency**: Natural frequency (for complex poles)
+
+A green dot marker will appear on the root locus curve to show exactly where your cursor is positioned.
+
+### Installation
+
+The interactive tools require matplotlib:
+
+```bash
+pip install matplotlib
+```
+
+### Examples
+
+See the `examples/` directory for more detailed examples:
+
+- `simple_rlocus_gui_example.py`: Basic usage
+
+### Comparison with MATLAB
+
+This GUI provides similar functionality to MATLAB's root locus tool:
+
+| Feature | MATLAB | Python Control |
+|---------|--------|----------------|
+| Hover information | ✓ | ✓ |
+| Grid lines | ✓ | ✓ |
+| Poles/zeros display | ✓ | ✓ |
+| Custom gain ranges | ✓ | ✓ |
+| Desktop application | ✓ | ✓ |
+| Jupyter integration | ✗ | ✓ |
+| Cursor marker | ✗ | ✓ |
+
+### Comparison with Existing Functionality
+
+The python-control library already has some interactive features:
diff --git a/control/interactive/__init__.py b/control/interactive/__init__.py
@@ -0,0 +1,30 @@
+"""
+Interactive plotting tools for the Python Control Systems Library.
+
+This module provides interactive plotting capabilities including root locus
+analysis with hover functionality.
+"""
+
+try:
+    from .rlocus_gui import root_locus_gui, rlocus_gui, root_locus_gui_advanced
+    __all__ = ['root_locus_gui', 'rlocus_gui', 'root_locus_gui_advanced']
+except ImportError as e:
+    def root_locus_gui(*args, **kwargs):
+        raise ImportError(
+            f"root_locus_gui could not be imported: {e}. "
+            "Make sure matplotlib is installed: pip install matplotlib"
+        )
+
+    def rlocus_gui(*args, **kwargs):
+        raise ImportError(
+            f"rlocus_gui could not be imported: {e}. "
+            "Make sure matplotlib is installed: pip install matplotlib"
+        )
+
+    def root_locus_gui_advanced(*args, **kwargs):
+        raise ImportError(
+            f"root_locus_gui_advanced could not be imported: {e}. "
+            "Make sure matplotlib is installed: pip install matplotlib"
+        )
+
+    __all__ = ['root_locus_gui', 'rlocus_gui', 'root_locus_gui_advanced']