`t0, tf`are the starting and ending times. They will generally be given with the problem.`x0vec`is the vector containing the initial -values for each equation in the system. They will generally be given with the problem.`initax`is the plot window sizing vector**only**for use with`pplane2d.m`. The first two entries correspond to the desired -range (horizontal). The second two entries correspond to the desired -range (vertical).`A`is the matrix of parameters associated with the linear part of the system.`B`is the matrix of parameters associated with the nonlinear part of the sytem (if any).`x1symb`is the symbolic solution to the first equation in the system; e.g., if a system for a 2nd order ODE,`x1symb`is the symbolic solution to the ODE. It must be entered in single quotes.`x2symb`is the symbolic solution to the second equation in the system; e.g., if a system for a 2nd order ODE,`x2symb`is the symbolic solution to the first derivative . It must be entered in single quotes.`x1symb`and`x2symb`are used for graphing, mainly with systems.`eqn_name`is the name of the MATLAB function M-file that describes the RHS of the system. It must be entered in single quotes AND without the`.m`extension.`symbolicplot`is the type of plot desired in the lower-left of`sys3plot`. Choosing``solutions'`will plot the symbolic solutions`x1symb`and`x2symb`wrt the time interval`t0`to`tf`. Choosing``phase'`will plot the two symbolic solutions`x1symb`and`x2symb`against each other in a phase plane plot. Choosing``eigenvals'`will plot the eigenvalues of the matrix . Choosing`''`will result in no plot in the lower-left. A choice is made by commenting out the others with a`%`at the beginning of each line containing the undesired options.- The rest of the entries in
`initsys.m`remain the same for all systems and cases. They are not changed by the user.