i'm trying to load a mat file from a subdirectory using the following code:
% filename_str is read from a text file
directoryname_str = "./data";
f = fullfile(directoryname_str, filename_str);
load(f);
when i run this sequence, load says it can't find the file...but when i copy or type the relative path and the file name by hand into an active octave session, everything works like a champ with no errors.
i assume this has something to do with how octave searches for mat files? if so, what's the correct environment variable or function call i need to make in order for this code to work?
thanks!
Are you sure that what you put into the variable f is the same as what you input manually in octave?
Are you also in the same directory? Because you're specifying relative paths, this should be the case.. you can get the current directory octave is in with pwd
And last of all, you can double check file existence in octave itself using exist
exist(f,'file')
If this returns false, there's definitely something wrong with your current directory, are something's very weird going on..
Related
I have placed a MATLAB script "x.m" in the path of my current working directory. So the script is in folder "~/a" and my working directory is "~/a/b"
But MATLAB seems to be not recognizing that the single function 'x' in the script exists? I have named the file exactly the same as function, which works properly when I place the script in my exact working directory rather than just on the path of my working directory. I believe my version is MATLAB2016a, if that makes any difference. Before updating to MATLAB2016a, I had made a similar function and was able to use it properly with just putting the script in the path of my working directory.
Suggestions/solutions?
You can't just have a function in the parent directory and expect MATLAB to find it. There is a thing called the MATLAB path, which is the collection of directories MATLAB will search to find functions. You can add directories to it using addpath.
My team is trying to standardise our Matlab paths so that everyone has the same.
I have a list of the default matlab path that we should all have.
So we would like to have a script that runs when matlab opens to make sure that our paths are set to the default matlab path. So if a path has been added to our default list it will be added in the correct place.
Is this possible in Matlab?
I read about startup but that seems to do with set your working directory which is different to what I am trying to do.
You can change which directory MATLAB starts in using the userpath function so that whenever you start up MATLAB, the path will automatically redirect here.
This may be useful if you have MATLAB running on a network per se, and multiple instances can start in the same network directory.
See more from MathWorks here: http://www.mathworks.com/help/matlab/matlab_env/matlab-startup-folder.html
However, if you want to standardize everything so that everyone has access to the same path, you can use startup to add directories / folders to MATLAB's path, but if you want to complete the package, use userpath to get MATLAB to start at a specified directory.
Your startup.m file may look something like this:
addpath('/folder/to/add/one');
addpath('/folder/to/add/two');
addpath('/folder/to/add/three');
addpath('/folder/to/add/four');
Then set your userpath with the function to complete everything:
userpath('/folder/to/start');
addpath('/folder/to/start');
Also make sure you add this new folder to your startup.m file too.
Include a path or addpath line in file startup.m. For example, to add folder aaa\bbb to the path the line would be
addpath('aaa\bbb')
Note that each user may have a different startup.m file. You may need to create it, if it doesn't already exist.
I have created a few general function in MATLAB that I intend to use for a few separate projects. However I do not want to copy the function into each separate project function.
I have created a folder called Misc_Function when I have placed these general functions. I know I can reference this functions explicitly by using the path and function name when trying to call the functions.
I believe you can add a path (in my case 'H:\MyTeam\Matlab\Misc_Function') when MATLAB loads up is that correct and if so how do you do this?
Assuming the above can be done I'm interested to know how MATLAB finds the correct function. In my understanding (guess work) MATLAB has a list of paths that it check trying to find a function with the name specified - is that correct? If so what happens when there are functions with the same name?
MATLAB indeed has its own search path which is a collection of folders that MATLAB will search when you reference a function or class (and a few other things). To see the search path, type path at the MATLAB prompt. From the documentation:
The order of folders on the search path is important. When files with the same name appear in multiple folders on the search path, MATLAB uses the one found in the folder nearest to the top of the search path.
If you have a set of utility functions that you want to make available to your projects, add the folder to the top of the search path with the addpath function, like so
addpath('H:\MyTeam\Matlab\Misc_Function');
You have to do this everytime you start MATLAB. Alternatively, and more conveniently, save the current search path with the savepath command or add the above commands to your startup.m file.
You can check the actual paths where Matlab searches for functions using
path
You will notice, that the most top path (on start up) is a path in your home folder. For Linux this is e.g. /home/$USER/Documents/MATLAB. For Windows it is somewhere in the the c:\Users\%USER%\Documents\Matlab (I think). Placing a file startup.m in this folder allows to add additional paths using
addpath('H:\MyTeam\Matlab\Misc_Function');
or
addpath(genpath('H:\MyTeam\Matlab\Misc_Function'));
on start up of Matlab. The latter (genpath) allows to also add all subdirectories. Simply write a file startup.m and add one of above lines there.
I believe 'addpath' will add the folder to MATLAB path only for the current MATLAB session. To save the updated path for other sessions, you need to execute 'savepath' command.
As mentioned in the previous comments, adding the folder in startup.m is a good idea since it will be added to the path on MATLAB startup.
To answer your question about how MATLAB finds the correct function, MATLAB maintains a list of directories in its path in a file called pathdef.m. Any changes to the path will be written to this file (when you execute 'savepath'). The path variable is initialized with the contents of this file.
In Matlab I defined a function called iReadImage it looks like:
function [outimag] = iReadImage(imaurl)
{code}
I used it for hours and everything seemed to work fine but then I changed one line and all of a sudden it didn't work anymore, even after I deleted that line nothing worked. It always tells me:
Attempt to execute SCRIPT iReadImage as a function:
/home/.../iReadImage.m
When I look at the file it says that it is 0kB....No idea why, I tried kind of everything, copied the function to a new function, rebooted my computer even tried it on other PCs. Two or three times it seemed to work again but never for long until I got the same error message.
Matlab is very particular about how its functions can be constructed. The file functionname.m should start with the first line function [output] = functionname(input). Otherwise, it will assume that it is dealing with a script and not a function. Additionally, if your file is a function, you can declare within it, like:
function y = f(x)
y = g(x) + 2;
function z = g(x)
z = x.^2;
end
end
However, if your file is a script, Matlab does not allow such function declarations. One way to test this would be to trivially turn your existing script into a function (by wrapping it with a function with null input and output), and see if he same error occurs.
The problem is probably that you've changed your working directory (using e.g. cd). You can only run functions that are in the current working directory, or in directories listed in path.
To confirm, type which iReadImage.
My guess is that you have multiple iReadImage files in the directories where matlab searches for scripts and functions. If so it's likley that Matlab have found the wrong one (perhaps one with an error in it?) and tries to execute it.
Make sure you only have one copy of the file (check which directories Matlab searches in with path).
To find out from which directory Matlab will execute your function write which <filename>, that is, in your case which iReadImage and make sure the correct file is used.
You can also use which iReadImage -all to find all iReadImage files.
I'm a total newbie to MATLAB but I have to write some code in it. I've had problems with making MATLAB see functions I've defined in external .m files. This is what I've done: I've created a file named, say, foo.m in my home dir with the following contents:
function [y] = foo(x)
% description
y = x + 1
When I run matlab (my home dir is matlab's workdir) it does not see foo function - it replies with standard ??? Undefined function or variable 'foo' message. BUT help foo or which foo return correct data printing help text and pointing on foo.m file respectively.
I must be missing something but I have no idea what it is. This is getting very annoying.
Oh, after several trial and error attempts I've managed to call that function. Unfortunately I can't remember the sequence of steps I've performed. Moreover after restarting matlab it returns to its usual 'Undefined function or variable' response.
I have 7.11.0.584 matlab running on linux.
MATLAB needs to be told which directories to search over to access those m-files. Clearly it cannot be left to search over your entire disk drives. The MATLAB search path is a list of directories that will be searched in specific order to find your functions.
help addpath
help pathtool
You should never put those files anywhere in the official MATLAB toolbox directories. Choose an entirely separate directory.
Finally, be careful not to name your own functions to match the names of existing MATLAB functions. Otherwise, your very next question here will be why your code does not work properly. This is a common cause of strange and confusing bugs.
It seems you're having some trouble with addpath. Try opening the file in the matlab editor and adding a break point in the file. If the file is not on Matlab's path, matlab should ask if you want to change directory or add the file to the path, choose add to the path.
If this doesn't work, try changing the current working directory (displayed in the main window) to the same location as the m file and calling the function. If this doesn't work you're either getting the name wrong ar there's possibly something wrong with your installation.
Occasionally matlab has problems if it does not have write permission to the directory the file's in, so check that too, i.e. make sure admin rights aren't required for the directory or m file.
Oh, and try:
clear functions
to reload all functions into memory.
The function needs to be in MATLAB's path. Use pathtool to tell MATLAB where to find your function. Note that if you name a function the same name as an existing function, MATLAB will use whichever function it finds first according to the order that the paths are listed as you see them in pathtool.
Although coming late but I hope it will help someone.
If in the folder where the function you are calling is residing, there is any other function with the same name as one of the functions from MATLAB toolboxes, then Matlab will not recognize its license and therefore will disable the whole folder from execution, no matter it is properly added to the path. The help will display though.
In order to check it, type:
which name_of_func.m
and you will get the path with "%Has no license available" message.
If it is your own function, you should not get this message but only the path.
Therefore, find the function in this folder which has the same name as a MATLAB toolbox functions, and rename it. I will solve the problem :).
Best Regards
Wajahat