Best way to rename a loaded variable?

Say that I have a .mat file that contains a variable, and I need to load this variable and give it a different name. Is there any other (/better) way to do this than:

load(myFile, myVar)
eval(['myNewname = ' myVar '; clear ' myVar])

?

[Jan]

Where does this EVAL idea come from? Did you find EVAL in the documentation or did you see it in an example?

I ask, because it is such frequently suggested to avoid EVAL in this and other Matlab forums for so many years, that I actually expect, that this method should be extinct already.

[Alec Nagel]

True -- I have seen such admonitions too. They might have been what prompted the question, on some subconscious level :) The idea came from the top of my head, and/or someone's code I read. Matt's solution seems so obvious in hindsight, but I don't think I'm alone in not having thought of it and, somewhat guiltily, having resorted to EVAL instead.

Answer 1

[Matt Fig]

Say you have the name of your variable:

VAR = 'S';

Now you want to load that variable, but with the name T. This method follows the general rule of thumb to avoid 'poofing' variables into the workspace.

T = load('myfile',VAR);  % Function output form of LOAD
T = T.(VAR)

[Alec Nagel]

That is a better way :)

[Maria Ironside]

Cool, so easy!

[Catriona Fyffe]

Nice, super helpful!

Answer 2

[Image Analyst]

I'd do it this way:

storedStructure = load(myFile, 'myVar'); % Load in ONLY the myVar variable.
myNewname = storedStructure.myVar;  % Assign it to a new variable with different name.
clear('storedStructure'); % If it's really not needed any longer.

Same net effect, it just uses the names Alec gave, and avoids dynamic structure fields, which are a bit advanced for beginners and not necessary here if you know the actual name.

Answer 3

[Stefano Petrò]

A way to do this in a single command is

myNewname = getfield(load(myFile,myVar),myVar);

[Steven Lord]

If you're using release R2019b or later you can use dot indexing into the output of function calls.

myVar = 'cdate';
C = load('census.mat', myVar).(myVar)

C = 21×1

1790 1800 1810 1820 1830 1840 1850 1860 1870 1880