Using MATLAB's plotting features as an interactive part of a Fortran program

Question

Although many of you will have a decent idea of what I'm aiming at, just from reading the title -- allow me a simple introduction still.

I have a Fortran program - it consists of a program, some internal subroutines, 7 modules with its own procedures, and ... uhmm, that's it.

Without going into much detail, for I don't think it's necessary at this point, what would be the easiest way to use MATLAB's plotting features (mainly plot(x,y) with some customizations) as an interactive part of my program ? For now I'm using some of my own custom plotting routines (based on HPGL and Calcomp's routines), but just as part of an exercise on my part, I'd like to see where this could go and how would it work (is it even possible what I'm suggesting?). Also, how much effort would it take on my part ?

I know this subject has been rather extensively described in many "tutorials" on the net, but for some reason I have trouble finding the really simple yet illustrative introductory ones. So if anyone can post an example or two, simple ones, I'd be really grateful. Or just take me by the hand and guide me through one working example.

platform: IVF 11.something :) on Win XP SP2, Matlab 2008b

Answer 1

The easiest way would be to have your Fortran program write to file, and have your Matlab program read those files for the information you want to plot. I do most of my number-crunching on Linux, so I'm not entirely sure how Windows handles one process writing a file and another reading it at the same time.

That's a bit of a kludge though, so you might want to think about using Matlab to call the Fortran program (or parts of it) and get data directly for plotting. In this case you'll want to investigate Creating Fortran MEX Files in the Matlab documentation. This is relatively straightforward to do and would serve your needs if you were happy to use Matlab to drive the process and Fortran to act as a compute service. I'd look in the examples distributed with Matlab for simple Fortran MEX files.

Finally, you could call Matlab from your Fortran program, search the documentation for Calling the Matlab Engine. It's a little more difficult for me to see how this might fit your needs, and it's not something I'm terribly familiar with.

If you post again with more detail I may be able to provide more specific tips, but you should probably start rolling your sleeves up and diving in to MEX files.

Answer 2

Dump Matlab because its proprietary, expensive, bloated/slow and codes are not easy to parallelize.

What you should do is use something on the lines of DISLIN, PLplot, GINO, gnuplotfortran etc.

Answer 3

Continuing the discussion of DISLIN as a solution, with an answer that won't fit into a comment...

@M. S. B. - hello. I apologize for writing in your answer, but these comments are much too short, and answering a question in the form of an answer with an answer is ... anyway ...

There is the Quick Plot feature of DISLIN -- routine QPLOT needs only three arguments to plot a curve: X array, Y array and number N. See Chapter 16 of the manual. Plus only several additional calls to select output device and label the axes. I haven't used this, so I don't know how good the auto-scaling is.

Yes, I know of Quickplot, and it's related routines, but it is too fixed for my needs (cannot change anything), and yes, it's autoscaling is somewhat quircky. Also, too big margins inside the graf.

Or if you want to use the power of GRAF to setup your graph box, there is subroutine GAXPAR to automatically generate recommended values. -2 as the first argument to LABDIG automatically determines the number of digits in tick-mark labels.

Have you tried the routines?

Sorry, I cannot find the GAXPAR routine you're reffering to in dislin's index. Are you sure it is called exactly like that ?

Reply by M.S.B.: Yes, I am sure about the spelling of GAXPAR. It is the last routine in Chapter 4 of the DISLIN 9.5 PDF manual. Perhaps it is a new routine? Also there is another path to automatic scaling: SETSCL -- see Chapter 6.

So far, what I've been doing (apart from some "duck tape" solutions) is

  use dislin; implicit none

  real, dimension(5) :: &
  x = [.5, 2., 3., 4., 5.], &
  y = [10., 22., 34., 43., 15.]
  real :: xa, xe, xor, xstp, &
          ya, ye, yor, ystp
  call setpag('da4p'); call metafl('xwin');
  call disini(); call winkey('return');

  call setscl(x,size(x),'x'); 
  call setscl(y,size(y),'y')

  call axslen(1680,2376) !(8/10)*2100 and 2970, respectively
  call setgrf('name','name','line','line')

  call incmrk(1); call hsymbl(3);

  call graf(xa, xe, xor, xstp, ya, ye, yor, ystp); call curve(x,y,size(x))
  call disfin()

  end

which will put the extreme values right on the axis. Do you know perhaps how could I go to have one "major tick margin" on the outside, as to put some area between the curve and the axis (while still keeping setscl's effects) ?

Even if you don't like the built-in auto-scaling, if you are already using DISLIN, rolling your own auto-scaling will be easier than calling Fortran from MATLAB. You can use the Fortran intrinsic functions minval and maxval to find the smallest and largest values in the data, than write a subroutine to round outwards to "nice" round values. Similarly, a subroutine to decide on the tick-mark spacing.

This is actually not so easy to accomplish (and ideas to prove me wrong will be gladly appreciated). Or should I say, it is easy if you know the rough range in which your values will lie. But if you don't, and you don't know whether your values will lie in the range of 13-34 or in the 1330-3440, then ...

... if I'm on the wrong track completely here, please, explain if you ment something different. My english is somewhat lacking, so I can only hope the above is understandable.

Inside a subroutine to determine round graph start/end values, you could scale the actual min/max values to always be between 1 and 10, then have a table to pick nice round values, then unscale back to the correct range.

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