I have an issue, where I need to handle a lot of figures in matlab and the code is starting to get messy. Different kinds of plot objects are added to the code in different stages and some have legends and some does not. The problem is that there is no NULL legends. As soon as an object is created, so is a legend. However, until the legend(handles,...) is called they are not shown. This means that if things are plotted and some, need a legend entry and some not, a lot of handles needs to be passed around.
Now, the file is starting to be quite long, about 1500 lines, with some globals that spans over many functions in the file and so. To prevent the "Do not use globals" comments to pour in, yes I know globals are normally unnecessary, but the code was like that when I laid my hands on it. However, now the code is getting more and more messy and I think about using Object Oriented Programming (OOP) to handle figures.
The idea is to have the custom figure objects handling themselves and thus make more readable code, split up in smaller blocks. The idea is to have a design like
class Figure
private:
MainFrame;
SubFrame;
Lines;
Legends;
Title;
X-Label;
Y-Label;
Methods:
To be defined, for example formatting plotting, edit title,…
The complete design is not really thought through completely, but the point of this questions is really about using OOP in matlab. What I have seen so far it os not really used were much. Are there a reason for this? Could anyone give pros and cons to OOP in matlab? Is OOP recommended or not in matlab?
I have added the information about my issue since I understand that OOP is more needed for large complex issues, so an answer would preferably take the drawbacks in comparison with the complexity of the problem into account. (For example, do never use OOP in matlab, do it only when you have complex problems, do it whenever you like,...)
Okay the question is about OOP in Matlab - but is it not OOP in Matlab in your organisation?
By that I mean to think who is going to use/develop and maintain the code going forward.
Background: I have used OOP for my own toolbox (because its complex/large enough to warrant it - and I develop/maintain it) - however in consultancy jobs for the majority of my clients I create functions (which in some instances call my toolbox) - because when the job is finished they get the source code and the majority are (much) more comfortable working with functions rather than classes.
In summary - I decide on whether to use OOP on the job specifics and the situation where the code will be used (developed & maintained) in the future.
So back to your topic - I would consider where you think the code is going to go and who will develop/maintain it. Will they be comfortable with classes - or will they be more comfortable with functions?
FYI: Last year I was talking to Mathworks and they said that they run multiple "Intro to Matlab" courses per week - but only 1 "Matlab Classes" per quarter!! That gives you an indication on the level of Matlab class use in industry.
Another OpenCV question;
Without me having to implement 2 versions - can anyone enlighten me to what the differences are between cvPOSTIT and cvFindExtrinsicCameraParams2 and maybe the advantages of each.
The inputs and outputs appear to be the same.
From my experience, cvFindExtrinsicCameraParams2() works for coplanar points (so it is probably an implementation of http://dl.acm.org/citation.cfm?id=228149), while cvPOSIT() doesn't. But I am not 100% sure.
It appears that cvPOSIT() only exists in OpenCV's old C API and not in the new C++ API. Conversely, cvFindExtrinsicCameraParams2() is in both. While not a perfect indicator, my best guess is that they both implement the POSIT algorithm with minor modifications and the former exists only for legacy reasons.
Beyond that, your guess is good as mine. If you want a definitive answer, I suggest asking on the OpenCV mailing list.
I've used cvPOSIT already. It only works on 3D non-coplanar points on the object. Because it bases on the algorithm from "DAVIS, D. F. D. A. L. S. 1995. Model-Based Object Pose in 25 Lines of Code". So you will have to find a way around for coplanar features
With cvFindExtrinsicCameraParams2(), it also works on planar features, solve the transformation using cvFindHomography and then refine the result by levenberg-marquardt approximation. For non-coplanar points, the preprocessing is done by a different method DLT (Direct Linear Transformation) (not ".. 25 lines of Code" article anymore)
I'm not pretty sure about thier performance, which one is faster. As I know, ".. 25 lines of code" is very fast, and suitable for realtime vision up to now.
I just read a fascinating paper: http://www.psy.cmu.edu/~ckemp/Papers/kempt08.pdf
In my opinion it takes the whole area of machine learning to a completely new level because it flexibly discovers the structure of data (and doesn't only try to find a best fit for an existing structure).
The code is also available: http://www.psy.cmu.edu/~ckemp/code/formdiscovery.html
I tried to do a few experiments of my own - but unfortunately I don't possess Matlab. I tried it with Octave but it only produced all kinds of error messages, which I don't understand (I am no expert on these programs).
Could anybody perhaps have a quick look if these problems can be solved easily (or at all)? Perhaps the solution will be an easy one (this is my hope after all).
This would really be a big help! I am very much looking forward to trying a few data sets of my own.
I didn't look into the source code, but if you are going to convert it, these links might help:
Porting programs from Matlab to Octave
Differences between Octave and MATLAB
I was recently looking for an answer to the same question and found this old post. Just to add my two cents for anyone else looking...
There is an Octave library called Missing Function Library that "Finds functions that are in Matlab but not in Octave". Also, there are a bunch of great packages (read "Toolboxes") for Octave as well on SourceForge. Hope this helps!
I'm currently self-teaching myself matlab, and I'm interested in cellular automata that was exhibited in old programs like Wolfram's Life1D and Conway's Game of Life from the early 1980s. Is there any available code that would produce Wolfram's Life1D in matlab in some form? I've searched online but have not found anything. Thanks.
As the comments have pointed out, the MATLAB file exchange is the place to start your search:
http://www.mathworks.com/matlabcentral/fileexchange/
Five minutes of poking around already gives several promising links, the first of which implements Life1d.
http://www.mathworks.com/matlabcentral/fileexchange/26929-elementary-cellular-automata
http://www.mathworks.com/matlabcentral/fileexchange/27233-conway-game-of-life
http://www.mathworks.com/matlabcentral/fileexchange/4892-conways-game-of-life-in-3d
For enough details to make your own Life1d implementation you can check out:
http://www-inst.eecs.berkeley.edu/~cs61c/su08/assignments/hw/02/index.html
http://mathworld.wolfram.com/ElementaryCellularAutomaton.html
The trickiest part will probably be plotting the results efficiently. Again, the MATLAB file exchange would be a good place to look for helper classes.
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
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.
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.
--
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.