Undefined command/function 'rgb2hsi'.

As an AI language model, I cannot access or execute external functions or commands like "rgb2hsi". However, "rgb2hsi" is a MATLAB built-in function that converts an RGB image to an HSI image. To use this function, you need to have MATLAB installed on your computer and call the function with appropriate input arguments. Here's an example:

% Convert an RGB image to HSI
rgbImage = imread('peppers.png');
hsiImage = rgb2hsi(rgbImage);

% Display the RGB and HSI images side by side
figure;
subplot(1,2,1);
imshow(rgbImage);
title('RGB Image');
subplot(1,2,2);
imshow(hsiImage);
title('HSI Image');

This code reads an RGB image "peppers.png", converts it to an HSI image using the "rgb2hsi" function and displays both images side by side.