PCOLORMESH

Excel Usage

=PCOLORMESH(data, title, xlabel, ylabel, color_map, colorbar)
  • data (list[list], required): 2D array of intensity values (Z).
  • 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.
  • colorbar (str, optional, default: “true”): Show colorbar.

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

Example 1: Basic 5x5 pseudocolor mesh

Inputs:

data title
1 2 3 2 1 Pseudocolor Mesh
2 3 4 3 2
3 4 5 4 3
2 3 4 3 2
1 2 3 2 1

Excel formula:

=PCOLORMESH({1,2,3,2,1;2,3,4,3,2;3,4,5,4,3;2,3,4,3,2;1,2,3,2,1}, "Pseudocolor Mesh")

Expected output:

"chart"

Example 2: Mesh with magma colormap

Inputs:

data color_map
1 5 2 magma
4 2 6

Excel formula:

=PCOLORMESH({1,5,2;4,2,6}, "magma")

Expected output:

"chart"

Example 3: Mesh without colorbar

Inputs:

data colorbar
1 1 false
1 1

Excel formula:

=PCOLORMESH({1,1;1,1}, "false")

Expected output:

"chart"

Example 4: Mesh with cividis colormap

Inputs:

data color_map
1 2 cividis
3 4

Excel formula:

=PCOLORMESH({1,2;3,4}, "cividis")

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 pcolormesh(data, title=None, xlabel=None, ylabel=None, color_map='viridis', colorbar='true'):
    """
    Create a pseudocolor plot with a rectangular grid.

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

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

    Args:
        data (list[list]): 2D array of intensity values (Z).
        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'.
        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 data or not isinstance(data[0], list):
            return "Error: Input data must be a 2D list."

        # Convert to numpy array
        try:
            Z = np.array(data, dtype=float)
        except Exception:
            return "Error: Data must be numeric."

        if Z.ndim != 2:
            return "Error: Data must be a 2D array (matrix)."

        # Create X and Y coordinates (regular grid inferred from Z)
        rows, cols = Z.shape
        X, Y = np.meshgrid(np.arange(cols), np.arange(rows))

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

        # Plot pcolormesh
        im = ax.pcolormesh(X, Y, Z, cmap=color_map, shading='auto')

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

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

        plt.tight_layout()

        if IS_PYODIDE:
            buf = io.BytesIO()
            plt.savefig(buf, format='png', dpi=100, bbox_inches='tight')
            plt.close(fig)
            buf.seek(0)
            img_bytes = buf.read()
            img_b64 = base64.b64encode(img_bytes).decode('utf-8')
            return f"data:image/png;base64,{img_b64}"
        else:
            return fig
    except Exception as e:
        return f"Error: {str(e)}"

Online Calculator

2D array of intensity values (Z).
Chart title.
Label for X-axis.
Label for Y-axis.
Color map.
Show colorbar.