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!
Related
I'm interested in hooking up AMPL with Matlab to obtain objective values, gradients, and Jacobians to test ideas for optimization algorithms on a wide set of problems. I'm aware that I can use amplfunc.mex or spamfunc.mex to do this; however, I'm having trouble compiling the .mex files using the old netlib files on Windows. The link also given in a previous question:
Using MATLAB with AMPL
is outdated. Does anyone know where I can obtain these .mex files or offer any alternative solutions? Thanks in advance.
The mex files amplfunc.c and spamfunc.c are still available at http://www.ampl.com/netlib/ampl/solvers/examples. We aren't aware of a reason why these wouldn't compile, but if you are having trouble you could write to the AMPL user forum, ampl#googlegroups.com. Be sure to explain which function you are using and to give the complete text of any error messages you see.
As you may know, extrinsic functions are not outputted during the code generation process. Are there alternatives to these functions and/or solutions to this problem? My code generation error report is shown below :
Code Generation Error Report
I am surprised that I can't output size and rgb2gray either. Since these are essential to my program, I cannot avoid them.
Help will be much appreciated!
This is a good question, and I see similar questions fairly frequently. As I started using MATLAB Coder, one of the biggest pitfalls was the constant search for supported functions. I sympathize with your frustration, and I have a few tips, having been through this.
First, to your direct question, while imread isn't supported by Coder, size and rgb2gray are. Probably Coder is complaining about these because they have been passed mxArrays from the call to imread, which is fine when it is extrinsic, but not ok for separate generation. That's just a guess. A very useful tool in writing code is the list of Coder supported functions: List of Functions supported in MATLAB Coder
But even with those two, to replace imread is not a tiny task. You'll have to find another library that supports the particular file you're working with, and then stitch that in using coder.ceval. Alternatively, if you can find a pure MATLAB implementation of it, that might help.
Are you targeting a pure C library or a MEX file? If you intend to use this code within the MATLAB environment, you can always use imread separately and then pass the data.
And now to some more general observations: MATLAB Coder isn't a perfect MATLAB to C translation system. It's extremely powerful, and I've been able to write some very large projects with it, but if what you want is the ability to run any MATLAB code without MATLAB around, you should look at MATLAB Compiler, a different add-on. There's a very good Q and A about this here: MATLAB Compiler vs MATLAB Coder
When writing projects in MATLAB Coder, it's really best to start from scratch, knowing you're targeting C code ultimately. There are so many gotchas in the conversion from MATLAB to C that you have to be always vigilant while writing the MATLAB code.
One tool that helps is to right-click on a file in the "Current Folder" list that usually resides on the left-side of the main window, and select "Check Code Generation Readiness." You'll get a great report of potential problems in the file. I recommend using this often.
Another useful tool is to always put the %#codegen tag into your code. This alerts the MATLAB editor that the .m file is intended for code generation, so it provides extra context-sensitive information while you're writing the file. This helps enormously.
The most commonly missing functions for code generation are file IO functions. There are some good reasons for this, but it's frustrating nonetheless.
When you stitch in external C code, you use the coder.ceval function, which can provide excellent access to external libraries. Using this well is a whole other topic, outside the scope of this question.
If you can indicate exactly what kind of files you're interested in reading (PNG, BMP, TIFF, etc.) perhaps someone may be able to identify a good external library for you to use.
so essentially I have the task to learn matlab decently well in the next few weeks, and I want to really be able to impress the people i'm learning it for, so if you guys have advice, I would greatly appreciate it.
What I'm dealing with Throughout the course of my job I will be dealing largely in two areas.
Formatting and importing data from excel
Interpreting the data in a meaningful way.
I realize the second category is extremely broad, but essentially i'm working with arrays of pricing information to set some standard price for a commodity, so the analysis that I will be doing will be less computationally heavy and will focus more on error getting the data in correctly and accurately and making sure all of the functions that I want to perform are executed correctly. Very basic stuff.
So here's what I'm looking for:
What are the most important topics so that I can import data from excel into matlab perfectly?
What should I study just to get basic functions down that will be applied to entire matrices/arrays?
What should I study prior to studying anything else to get a firm foundation in the subject? (So I don't make stupid syntax errors, etc.)?
Your help is greatly appreciated :)
The first two things you'll want to learn about are (1) the Matlab GUI and (2) the basics of Matlab syntax. A quick visit to the Getting Started section of the Matlab documentation will do you wonders. It should take you less than a day to get through the basics. Do note that the Matlab documentation is generally excellent, and you should use it often.
Beyond that, there are a number of questions here about importing Excel into Matlab (importing from excel, exporting to excel), and there's some excellent docs on the Mathworks site as well (xlsread, xlswrite). Read them and become familiar with the details and common problems. Good luck!
Since you will be using excel it is likely the data you import could come out in cell format. Look into the differences between indexing using matrices and cells. Also, learn early on the difference between [operator] and .[operator] for vector calculations. The second one is element-wise and will most likely solve a lot of issues you'll come across if your records are meant to only relate to one row/column of data
Perhaps you have gained the MATLAB skills you need now, but hopefully this will help someone following the same path later.
The Math Works (developers of MATLAB) run a site called MATLAB Cody.
This site offers a range of problems and a web based MATLAB interpreter so you can test your solutions. When you have a correct solution, you can compare with other solutions to the same problem. Then you can look up the functions others have used in the online MATLAB documentation for more understanding.
The problems focus on regular expressions and cell manipulation which will be very relevant to importing and manipulating Excel data.
I am about to start a project in visual image-processing and have no had experience with Matlab, Aforge, OpenCV and was wondering if anyone had any experiences with these different software packages.
I was also wondering which of the three packages were most efficient I assume OpenCV but has anyone had any experience?
Thanks
Jamie.
The question you need to ask yourself is which is more important - your time or the computer's time. If your task is really simple, you may be able to code it up in MATLAB and have it work right off the bat. MATLAB is by far the easiest for development - a scripted language with built-in memory management, a huge array of provided functions, and a great interface for displaying and manipulating data while debugging.
On the other hand, MATLAB is at least an order of magnitude slower than compiled openCV code for many tasks. This is especially true if you use the intel performance primitives libraries.
If you know how to code in MATLAB, I would suggest writing and debugging your algorithms in that language, then porting them to c/c++ with openCV for speed. If there are only a couple of simple functions that you need to speed up, you can call c code from MATLAB, but it's hard to get this working right the first few times you try it, so you're probably better off just rewriting your finished code entirely in c/c++
First, please elaborate about your project's needs. It has the biggest impact on the choice, in addition to other factors - your general programming knowledge (If you haven't dealt with dot net but just with C++, AForge is not a good choice, for example).
Generally,
Both AForge and OpenCV has a built-in interface to .Net, and OpenCV also with C++, python, and more. Matlab might be more efficient, but if you don't have any experience with it - you should also learn its syntax. Take it into consideration.
Matlab probably has the largest variety of functions, but it is more complicated than the other projects. OpenCV and AForge themselves have some differences - see them described in this StackOverflow question/ answers.
I worked last year in two similar projects with cars on the highway. Afaik, Matlab allows to process only one picture frame at a time (surely you could elaborate an algorithm to compute a stream) but using Simulink you can process the stream directly.
On the other hand, i found AForge a lot friendlier and easier to use since you can easily adjust the processing parameters from a GUI (not so fast/easy) to do in Matlab/simulink.
I'd go for Aforge.Net. It's also fast enough if you're worrying about processing speed. (using 640x480)
If you are asking about using one of these in .net,easily you can get info by this:
1-matlab mostly used in simulation of projects not the End-prototype project; my numer : 30;
2-aforge (as I'v used in many project) if you do not need the circular process like capturing image, or recognition of something in images or ... you'll find it very good, cause it is easy to use but useful for single processes; my number : 50
3-opencv very good at speed and useful for circular processes, for example you can capture images from a webcam and Instantly cartoonize it without any delay, But not easy-to-use as aforge. I like it anyway cause of its speed and MANY functions it gives us mostly anything we need in programming; my number : 80
Dr.Taha - Tahasoft.net
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.