using kmeans to convert rgb image to grayscale

I have a rgb image, I want to use kmeans to convert rgb image to grayscale. can you help me, please?

Answer 1

[Image Analyst]

Why kmeans() specifically? Why not just use rgb2ind()?

[nguyen tien]

oh. my project must be used kmeans. my subject is image recognition using kmeans.

[Image Analyst]

How is simply converting to grayscale "recognition"???

Anyway, see the MATLAB demo for image segmentation using kmeans: http://www.mathworks.com/examples/image/2068-color-based-segmentation-using-k-means-clustering

[John D'Errico]

I'm not at all sure I see how kmeans is intended to be used for an RGB - gray scale conversion. kmeans is a clustering algorithm. As such, it would have no value for your project.