You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: b2r.m
    path of file: ./repos/PIDtoolbox
    
    the code of the file until where you have to start completion: function newmap = b2r(cmin_input,cmax_input)
%BLUEWHITERED   Blue, white, and red color map.
%   this matlab file is designed to draw anomaly figures. the color of
%   the colorbar is from blue to white and then to red, corresponding to 
%   the anomaly values from negative to zero to positive, respectively. 
%   The color white always correspondes to value zero. 
%   
%   You should input two values like caxis in matlab, that is the min and
%   the max value of color values designed.  e.g. colormap(b2r(-3,5))
%   
%   the brightness of blue and red will change according to your setting,
%   so that the brightness of the color corresponded to the color of his
%   opposite number
%   e.g. colormap(b2r(-3,6))   is from light blue to deep red
%   e.g. colormap(b2r(-3,3))   is from deep blue to deep red
%
%   I'd advise you to use colorbar first to make sure the caxis' cmax and cmin.
%   Besides, there is also another similar colorbar named 'darkb2r', in which the 
%   color is darker.
%
%   by Cunjie Zhang, 2011-3-14
%   find bugs ====> email : daisy19880411@126.com
%   updated:  Robert Beckman help to fix the bug when start point is zero, 2015-04-08
%   
%   Examples:
%   ------------------------------
%   figure
%   peaks;
%   colormap(b2r(-6,8)), colorbar, title('b2r')
%   


%% check the input

    
function newmap = b2r(cmin_input,cmax_input)
%BLUEWHITERED   Blue, white, and red color map.
%   this matlab file is designed to draw anomaly figures. the color of
%   the colorbar is from blue to white and then to red, corresponding to 
%   the anomaly values from negative to zero to positive, respectively. 
%   The color white always correspondes to value zero. 
%   
%   You should input two values like caxis in matlab, that is the min and
%   the max value of color values designed.  e.g. colormap(b2r(-3,5))
%   
%   the brightness of blue and red will change according to your setting,
%   so that the brightness of the color corresponded to the color of his
%   opposite number
%   e.g. colormap(b2r(-3,6))   is from light blue to deep red
%   e.g. colormap(b2r(-3,3))   is from deep blue to deep red
%
%   I'd advise you to use colorbar first to make sure the caxis' cmax and cmin.
%   Besides, there is also another similar colorbar named 'darkb2r', in which the 
%   color is darker.
%
%   by Cunjie Zhang, 2011-3-14
%   find bugs ====> email : daisy19880411@126.com
%   updated:  Robert Beckman help to fix the bug when start point is zero, 2015-04-08
%   
%   Examples:
%   ------------------------------
%   figure
%   peaks;
%   colormap(b2r(-6,8)), colorbar, title('b2r')
%   


%% check the input
if nargin ~= 2 ;
   disp('input error');
   disp('input two variables, the range of caxis , for example : colormap(b2r(-3,3))');
end