GANTT

Excel Usage

=GANTT(data, title, xlabel, ylabel, color_map, legend)

• data (list[list], required): Input data (Labels, Start, Duration).
• title (str, optional, default: null): Chart title.
• xlabel (str, optional, default: null): Label for X-axis.
• ylabel (str, optional, default: null): Label for Y-axis.
• color_map (str, optional, default: “viridis”): Color map for tasks.
• legend (str, optional, default: “false”): Show legend.

Returns (object): Matplotlib Figure object (standard Python) or base64 encoded PNG string (Pyodide).

Examples

Example 1: Project timeline with multiple tasks

Inputs:

data
Design	0	5
Development	4	10
Testing	12	4
Deployment	15	2

Excel formula:

=GANTT({"Design",0,5;"Development",4,10;"Testing",12,4;"Deployment",15,2})

Expected output:

"chart"

Example 2: Gantt with custom axis labels and title

Inputs:

data			title	xlabel	ylabel
Phase 1	0	3	Project Schedule	Days	Tasks
Phase 2	2	4

Excel formula:

=GANTT({"Phase 1",0,3;"Phase 2",2,4}, "Project Schedule", "Days", "Tasks")

Expected output:

"chart"

Example 3: Gantt with legend

Inputs:

data			legend
Task A	0	5	true
Task B	3	6

Excel formula:

=GANTT({"Task A",0,5;"Task B",3,6}, "true")

Expected output:

"chart"

Example 4: Custom color map

Inputs:

data			color_map
Sprint 1	0	14	plasma
Sprint 2	14	14
Sprint 3	28	14

Excel formula:

=GANTT({"Sprint 1",0,14;"Sprint 2",14,14;"Sprint 3",28,14}, "plasma")

Expected output:

"chart"

Python Code

import sys
import matplotlib
IS_PYODIDE = sys.platform == "emscripten"
if IS_PYODIDE:
    matplotlib.use('Agg')
import matplotlib.pyplot as plt
import io
import base64
import numpy as np

def gantt(data, title=None, xlabel=None, ylabel=None, color_map='viridis', legend='false'):
    """
    Create a Gantt chart (timeline of tasks).

    See: https://matplotlib.org/stable/api/_as_gen/matplotlib.axes.Axes.broken_barh.html

    This example function is provided as-is without any representation of accuracy.

    Args:
        data (list[list]): Input data (Labels, Start, Duration).
        title (str, optional): Chart title. Default is None.
        xlabel (str, optional): Label for X-axis. Default is None.
        ylabel (str, optional): Label for Y-axis. Default is None.
        color_map (str, optional): Color map for tasks. Valid options: Viridis, Plasma, Inferno, Magma, Cividis. Default is 'viridis'.
        legend (str, optional): Show legend. Valid options: True, False. Default is 'false'.

    Returns:
        object: Matplotlib Figure object (standard Python) or base64 encoded PNG string (Pyodide).
    """
    def to2d(x):
        return [[x]] if not isinstance(x, list) else x

    try:
        data = to2d(data)

        if not isinstance(data, list) or len(data) == 0:
            return "Error: Data must be a non-empty 2D list"

        # Extract labels, starts, and durations
        labels = []
        starts = []
        durations = []

        for row in data:
            if not isinstance(row, list) or len(row) < 3:
                continue

            try:
                label = str(row[0]) if row[0] else "Task"
                start = float(row[1])
                duration = float(row[2])

                if duration <= 0:
                    continue

                labels.append(label)
                starts.append(start)
                durations.append(duration)
            except (TypeError, ValueError):
                continue

        if len(labels) == 0:
            return "Error: No valid task data found"

        # Create the figure
        fig, ax = plt.subplots(figsize=(10, max(4, len(labels) * 0.6)))

        # Get colormap
        try:
            cmap = plt.get_cmap(color_map)
            colors = [cmap(i / len(labels)) for i in range(len(labels))]
        except:
            colors = ['steelblue'] * len(labels)

        # Create Gantt chart using horizontal bars
        y_pos = np.arange(len(labels))

        for i, (start, duration, color, label) in enumerate(zip(starts, durations, colors, labels)):
            ax.barh(i, duration, left=start, height=0.6, color=color, 
                    edgecolor='black', linewidth=0.5, label=label if legend == "true" else None)

        ax.set_yticks(y_pos)
        ax.set_yticklabels(labels)
        ax.invert_yaxis()

        if xlabel:
            ax.set_xlabel(str(xlabel))
        else:
            ax.set_xlabel('Time')

        if ylabel:
            ax.set_ylabel(str(ylabel))

        if title:
            ax.set_title(str(title))

        if legend == "true":
            ax.legend(loc='best', fontsize='small')

        ax.grid(True, axis='x', alpha=0.3)
        plt.tight_layout()

        if IS_PYODIDE:
            buf = io.BytesIO()
            plt.savefig(buf, format='png', dpi=100, bbox_inches='tight')
            buf.seek(0)
            img_base64 = base64.b64encode(buf.read()).decode('utf-8')
            plt.close(fig)
            return f"data:image/png;base64,{img_base64}"
        else:
            return fig
    except Exception as e:
        return f"Error: {str(e)}"

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