HEATMAP

Excel Usage

=HEATMAP(data, title, xlabel, ylabel, color_map, values, colorbar)

• data (list[list], required): Input matrix data.
• 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.
• values (str, optional, default: “false”): Show values.
• colorbar (str, optional, default: “true”): Show colorbar.

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

Examples

Example 1: Basic 3x3 heatmap

Inputs:

data
1	2	3
4	5	6
7	8	9

Excel formula:

=HEATMAP({1,2,3;4,5,6;7,8,9})

Expected output:

"chart"

Example 2: Heatmap with title and labels

Inputs:

data		title	xlabel	ylabel
1	2	My Heatmap	X	Y
3	4

Excel formula:

=HEATMAP({1,2;3,4}, "My Heatmap", "X", "Y")

Expected output:

"chart"

Example 3: Heatmap with plasma colormap

Inputs:

data			color_map
1	2	3	plasma
4	5	6

Excel formula:

=HEATMAP({1,2,3;4,5,6}, "plasma")

Expected output:

"chart"

Example 4: Heatmap showing values

Inputs:

data		values
1.5	2.5	true
3.5	4.5

Excel formula:

=HEATMAP({1.5,2.5;3.5,4.5}, "true")

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 heatmap(data, title=None, xlabel=None, ylabel=None, color_map='viridis', values='false', colorbar='true'):
    """
    Create a heatmap from a matrix of data.

    See: https://matplotlib.org/stable/api/_as_gen/matplotlib.pyplot.imshow.html

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

    Args:
        data (list[list]): Input matrix data.
        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. Valid options: Viridis, Plasma, Inferno, Magma, Cividis. Default is 'viridis'.
        values (str, optional): Show values. Valid options: True, False. Default is 'false'.
        colorbar (str, optional): Show colorbar. Valid options: True, False. Default is 'true'.

    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 not all(isinstance(row, list) for row in data):
            return "Error: Invalid input - data must be a 2D list"

        # Convert to numpy array
        try:
            arr = np.array(data, dtype=float)
        except (ValueError, TypeError) as e:
            return f"Error: Could not convert data to numeric array: {str(e)}"

        if arr.ndim != 2:
            return "Error: Data must be a 2D array"

        if arr.size == 0:
            return "Error: Data array is empty"

        # Create figure
        fig, ax = plt.subplots(figsize=(8, 6))

        # Create heatmap
        im = ax.imshow(arr, cmap=color_map, aspect='auto')

        # Add colorbar if requested
        show_colorbar = colorbar.lower() == "true"
        if show_colorbar:
            plt.colorbar(im, ax=ax)

        # Add values if requested
        show_values = values.lower() == "true"
        if show_values:
            for i in range(arr.shape[0]):
                for j in range(arr.shape[1]):
                    text = ax.text(j, i, f'{arr[i, j]:.2f}',
                                 ha="center", va="center", color="white")

        # Set labels
        if title:
            ax.set_title(title)
        if xlabel:
            ax.set_xlabel(xlabel)
        if ylabel:
            ax.set_ylabel(ylabel)

        plt.tight_layout()

        # Return based on environment
        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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