using backend code of matlab commands for creating new command

Rise time is to be calculated using basic matlab (excluding all toolboxes) in a generalised manner.

how can i modify the code available in SPT in order to generalise it?

i need to calculate rise time for each pulse in a multi pulsed waveform.

[SHANTANU KSHIRSAGAR]

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