read few lines from one *.m file and jump to another *.m file

Is it possible to read only few lines from one matlab code and then jump to another matlab code and read there another few set of lines and so on?

Answer 1

[Jan]

This is not the purpose of program code. If you need only some lines of a specific function, create a copy of this functions and remove the other lines. Fortunately there are no magic GOTO or COMEFROM commands in Matlab. Reading the files by fileread and evaluating some lines by eval is a very bad idea also, because you would create a Meta-Matlab-Interpreter, which is too indirect and prone to bugs to be used efficiently.

[Stephen23]

MATLAB users also miss out on the endless delights offered by JUMPOVER, SKIPAROUND, IGNOREERROR, PLEASE, GOFROM, and COMETO (the latter two only work with multithreaded execution). Come to think of it, some of these are still used in Microsoft's venerable VBA!

And of course we are still waiting for the much requested DOWHATIWANTANDNOTWHATIWROTE command.

[Megha]

I believe, there has to be some function to execute only few lines from a given matlab code. When dealing with the huge data sets. Matlab is running out of memory and hence not advisable to load all files and run full code...

[Jan]

@Megha: You can select a block of code in the editor and run it specifically. But therefore the required variables must be existing before already, so this is rarely useful.

I do not understand, why running a few lines of code helps to deal with large data sets. "Loading all files" and "running all codes" sounds like two different jobs - except if the code consists of a list of load commands. But even then it sounds very easy to modify the script or function by editing it. E.g. a block comment or a if 0 ... end should be useful. Or maybe a control like:

function Data = YourCode(WhatToLoad)
switch WhatToLoad
  case 'all'
    Data{1} = load('asd.mat');
    Data{2} = load('other.mat');
  case 'firstOnly'
    Data{1} = load('asd.mat');
end

You see, no magic meta-commands required. if else or switch case are enough to control what is executed.

@Stephen: I have implemented PLEASE as mex function. It evaluates the provided function handle and arguments, but strings also. So it is a polite version of feval and eval. I do not publish it in the FileExchange to avoid being reminded to read Tutorial: Why to avoid EVAL.

DOWHATIWANTANDNOTWHATIWROTE is implemented as feature('dwim') already.

[Megha]

@Jan, let me rephrase my question:

i have first.m file and it contains let us say 50 lines code
  and I have second.m file that contains 30 lines code. 
Now I open third.m file and would like to run line 2:10
from first.m file and then I direct it to a second.m file
and there i want to run line 5:20.

So, is there any command to run only the desired lines from the matlab code?

run('scriptname.m') command helps running given script but it will run whole script. However, I want only few lines from the script.

Thank you very much for your help @ Jan, @ stephen .

[Stephen23]

@Megha: no, there is not easy way to do that. It would be possible using some highly inefficient, slow, and likely buggy file reading and evaluation, but that would be an incredibly bad way to run code, and I would not recommend doing that. That is why Jan has also been advising you to use standard control statements, e.g. if or switch. Standard control statements are simple, efficient, and easy to debug. In fact that is exactly what control statements are for: for controlling which code runs. You should use them.

You should avoid doing the kind of magic that you are trying to do.

[Megha]

@Stephen: Thank you very much for your response. I will go with your suggestion.