Retrieve a variable previous value in the console

Hello Guys, an easy question. Does anybody know a trick to recover a previous variable value in the console. Lets say that a variable has a stored value (a=3 - it may be a very long vector, matrix, etc and any value) and then it is modified (accidentally) to a new value (a=4). Is there any way to recover the previous value that the variable a had stored? i) immediately after screw it over, something link an undo, ii) after some console commands. Cheers,

[Craig]

hope this gets fixed

[Guillaume]

If what get fixed? If you're talking about the behaviour described in the question, it's not going to get fixed as there's nothing to fix. This is the way computers behave. Once you put something in memory, it replaces whatever was there previously. Keeping the previous value around would mean storing the previous value somewhere else, making your computer twice as slow while letting you use only half its memory.

Answer 1

[Walter Roberson]

Sorry, no, other than starting over or (if you know the values) assigning the values back by hand.

Answer 2

[Iain]

It may still be in the command history. If so you just need to look at the command history, and drag, (or select and hit enter or copy + paste) the lines of code into your command window and hit enter.

The up cursor button will go through it line by line - handy for something like b = areallylongfunctionname('areallylongpath, ... ... .. ... ,2);

[Walter Roberson]

Also if you type the first few letters of a command and up-arrow then it will take you back to the command that starts with what you typed.

Answer 3

[Leonabil]

Thanks for your answers. The problem is that I do not have available the command and the numerical value on the variable. Indeed, the variable is a matrix array resulting of a very long iteratively optimisation problem lost by typing mistake. Then, getting back in the command history unfortunately does not work, so I was wondering if Matlab has something linke a variable repository memory where I can recover a previous variable value not recurring to the command history or manual entry :-( I am afraid that I need to run the whole process again and this time save the variable - just in case. Thanks for your answers.

[Walter Roberson]

Sorry, no, once you overwrite a variable it is gone. There is no UNDO for an assignment.