cmap_sweep.m

% CMAP_SWEEP A function to set the color order of plot to sweep through n colors.
% Timothy Sipkens, 2020-06-26
%
% Inputs:
%   n         The number of lines that will be plotted / colors to sweep through.
%   cm        Colormap that is used to specify the ColorOrder.
%=========================================================================%

function [cm2] = cmap_sweep(n, cm)


if ~exist('cm','var'); cm = []; end
if isempty(cm); cm = colormap('gray'); end % by default use grayscale


% Determine positions in colormap to use.
% Method varies depending on n.
if n == 1
    cm2 = cm(round(size(cm,1) / 2), :);

elseif n < 8  % span full lengths of colormap (expects long colormap)
    n1 = round((0:(n-1)) ./ (n-1) .* ...
        (size(cm,1) - 1)) + 1;
    cm2 = cm(n1, :);

else  % index existing colormap entries
    n1 = floor(size(cm, 1) / n); % interval between colormap indices
    n2 = length(cm) - n*n1 + 1;   % starting index, i.e. mod(cm,n) does not always equal 0
    cm2 = cm(n2:n1:end, :);    % adjust colormap to appropriate size
end

set(gca,'ColorOrder',cm2,'NextPlot','replacechildren');
    % set ColorOrder for current axis

    
if nargout==0; clear cm2; end % suppress output if none required

end