Visualize matrix by a heatmap

% PCOLORMAT allows you to visualize the matrix with color gradient
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% USAGE:
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% pcolorMat(mat,ncolor,ndigits)
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% INPUT:
% - mat: The matrix you want to visualize
% - ncolor: number of color gradient
% - ndigits: number of decimal digits shown in the figure.
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% OUTPUT:
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% EXAMPLES:
% pcolorMat(rand(4,4))
% pcolorMat(rand(4,4),4)
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% Copyright 2015. Zhang (Frank) Cheng (zhangc518@gmail.com
% v:1.0 22 May 2015. Initial release.
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% Dependence:
% colorGradient.m: http://www.mathworks.com/matlabcentral/fileexchange/31524-colorgradient--generate-custom-linear-colormaps/content/colorGradient.m