More details on paths in MATLAB

Transcription

1 More details on paths in MATLAB Water & People in a changing world, Yhd In the hands-on session 1, we handled setting the path a bit too quickly and didn't sufficiently take different operating systems into account. Sorry for that, hope it didn't cause too many difficulties for you! Here is some additional information and step-by-step instructions how to find the path of your working directory. General It is important to know your current working directory where your scripts are stored and data is saved with save function, and to define the search path in the MATLAB, as programs use that to find scripts, functions and data. The working directory This refers to the working folder of a session in question (in this case the specific hands-on training folder). The current directory is the one you see in the address bar and whose contents are in the Current Folder window, and to where save command stores the data. You go to your working directory with following command (replace the path in the command with the one you have your data in): cd('z:\documents\waterandpeople\handson1'); % in windows cd('/users/mkummu/documents/studies/waterandpeople/handson1'); % in Mac OS The search path This defines the directories that are in the search path(replace the path in the command with the one you have your data in): addpath(genpath('z:\documents\waterandpeople)); % in windows addpath(genpath('/users/mkummu/documents/studies/waterandpeople')); % in Mac OS Note that here the command refers to the main course directory, in this case the folder where all hands-on session data and scrips are stored in. We use subdirectories like the handson1, handson2 etc, and all of them are automatically added to the path with this one command. Also, you may notice some directories in the Current Folder window are in grey font, other are black. The ones in black belong to the path, and the grey ones do not. How to name the folder and files Please avoid spaces in file and folder names, either write everything together or use _ to separate words. And aim to keep them short, but still so that you recognise what is in where. How do you find the full path to a directory When you create a new folder for example under your My Documents folder and want to use the corresponding directory in your MATLAB work, you need to know the full path. Below are examples of how you can do it in Windows and in OS X (Mac).

2 Windows example First, when you open the folder in the Windows explorer (the file manager), you see the folder names in the address bar at the top. Click the empty area to the right of the folder names: The folder names change to a path string that you can copy into MATLAB:

3 OS X (Mac) example Please note that this example is for El Capitan (OS X 10.11). For other versions of the operating system, please refer to 1. Go to target folder 2. RIGHT-CLICK the document/folder in the Finder and keep your mouse icon over the Copy option. (Do NOT click the mouse button to select this option yet)

4 3. Whilst still keeping your mouse over the Copy contextual menu option, hold down the ALT/OPTION key. The Copy option changes to Copy as Pathname. This copies the full path to the file into the OS X clipboard. You can then paste this full pathname anywhere you like.

5 Setting the path There are several functions in MATLAB that allow you to manage the path. The most important one is addpath. It simply adds the specified directories at the top of the path. Being at the top means that these directories are searched first. addpath('z:\documents\waterandpeople\'); addpath('/users/username/documents/waterandpeople/'); % Note the different delimiter characters, \ in Windows, / in Mac It is a very good idea to avoid using spaces in the names of directories and files. If you really need them (for example, your existing directory structure already has them in a higher level), the functional forms of file management commands will work, but you need to quote the strings also for command forms: load('my datafile.mat') load 'my datafile.mat ' % this is the functional form % this is the command form The maximum length of a full directory name in MATLAB path is 260 characters. It is a good idea to keep your directory and file names short you never know how many levels of subdirectories you end up needing. Setting the path to a directory tree If you want to add a whole tree (directory and all of its subdirectories) into your path, you need the genpath function. It will create a string with all the required directory names and you can use that in addpath: addpath(genpath('z:\documents\waterandpeople\')); addpath(genpath('/users/username/documents/waterandpeople/')); After this, your path has one entry for the WaterAndPeople directory and one entry for each of its subdirectories. Changing your working directory After you set your path, MATLAB will find the files in those directories when you run a command that needs them. But to actually change the working directory so that you see the contents in the Current Folder window and your save commands will create files in that location, you use cd. cd('z:\documents\waterandpeople\handson1'); cd('/users/username/documents/waterandpeople/handson1');