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# File

- (P)rt info
  This creates a new window which contains the complete source of the ODE file. If you click on the Action and have defined some action associated with it, then this is how to execute it. Click on Source to get back the original ODE file.
- (W)rite set
  This creates a file with all of the info about the current numerics, etc as well as all of the currently highlighted graphics window. It is easily readable by the user and essentially saves the current state of XPP to be read in later.

- (S)ave info
  This is like (P)rt info but saves the info to a file. It is human readable but not nearly as comprehensive as the files saved by Write set.

- (A)uto
  This brings up the AUTO window if you have installed it.

- (C)alculator
  This pops up a little answer window. Type formulae in the command line involving your variables and the results are displayed in the popup.

  To set an initial condition or parameter type `x:exp(-1)`, for example, to set the parameter or variable, `x` to `exp(-1)` .

  To exit the calculator, click on Quit in the answer window or type Esc.

- (R)ead set
  This reads a set that you have previously written with the Write set command. The files is very tightly connected to the ODE file that wrote it, so you should not try to load a saved file from one equation for a different problem or even the same one if you have altered the ODE file.

- (Q)uit
  This exits XPP first asking if you are sure.

- (E)dit
  You can edit the equations from within XPP. Note: XPP is capable of understanding right-hand sides of up to 1000 characters. However, the RHS editor will not accept anything longer than about 72 characters. This menu item presents a list of four options:

  - (R)HS
    Edit the right-hand sides of the ODEs IDEs, and auxiliary variables. If you are happy with the editing, then type TAB or click on OK. The program will parse the new equations and if they are syntactically correct, alter the corresponding equation. If there is an error, the you will be told of the offending right-hand-side and that will not be changed.

  - (F)unctions
    This lets you alter any user-defined functions. It is otherwise the same as the above.

  - (S)ave as
    This creates an ``ODE'' file based on the current parameter values, functions, and right-hand sides. You will be asked for a filename.

  - (L)oad DLL
    On systems which allow dynamically linked libraries, you can load in a compiled version of right-hand sides for your ODE. See linking to C for examples.

- (B)ell on/off
  This toggles the stupid noisy bell on and off.

- (T)ranspose
  This allows you to transpose data in the data browser. You may want to do this is you are solving a discretization of a PDE and want to see solutions at a fixed value of time plotted as a function of index. A dialog box comes up asking for
  - the first column
  - the total number of columns
  - the skip between columns (eg every 3 cols)
  - the first time slice as a row number
  - the number of rows
  - skip between rows (e.g. every 10th row)

  Suppose you have data of the form [u1(t),...,u20(t)] fort=0,0.05, ..., 20.00 in the data browser. You thus have 401 rows of data. Then if you choose u1 as the first column, 20 as the number of columns, 1 for the column skip, 100 as the first row, 10 as the number of rows, and 20 as the row skip, the data in the "time" column of the browser is replaced by the numbers 1 to 20 representing the index; the column for "u1" is replaced by

  [u1(t1),u2(t1),...,u20(t1)]

  where t1=100*0.05 . The tenth column,"u10", is replaced by

  [u1(t10),u2(t10),...,u20(t10)]

  where t10=100*0.05 + 10*20*0.05 since you chose to skip every 20 rows.