function [r,lwrCross,uprCross,lwrRef,uprRef] = risetime(x, varargin);
if nargin > 1
[varargin{:}] = convertStringsToChars(varargin{:});
end
% plot if no output specified
plotFlag = nargout==0;
% obtain durations and crossings for all positive-going transitions
[r,lwrCross,uprCross,lwrRef,uprRef] = transdurs(x,1,plotFlag,varargin{:});
how do i modify this function for the same