Undefined function or variable when using load and trying to operate with variables

Hi: I have posted before asking one question and I didn't really explain myself correctly so not ALL my question was solved: I have a function which saves some variables each time with a different name in the form of a matrix (30x30). This variables are called Z_1,Z_2,Z_3,etc...

save(['Z_' num2str(v)],'z')

Now I want to add these variables which I have created (Z_1,Z_2,etc) so that it gives me a matrix (30x30) called TotalZ for example. This would be done easily enough using:

load('C\wherever.the.variable.is.stored\Z_1');
load('C\wherever.the.variable.is.stored\Z_2');
load('C\wherever.the.variable.is.stored\Z_3');

TotalZ=Z_1+Z_2+Z_3;

But every time I try running this I get the error;

??? Undefined function or variable 'Z_1'.

Error in ==> mapa at 31
     TotZ=Z_1+Z_2+Z_3

I am getting a bit frustated as I have clearly defined my variables and loaded them properly (or so I think) so I see no reason for this error. The idea would then be to plot the TotalZ against two variables with a pcolor plot.

Thanks for any help. Guillermo

[Guillermo Lopez]

And it might be a problem as every time it is loaded into the workspace all variables Z_1,Z_2,Z_3 are named the same (z) due to the name of the variable being saved so I suppose every time I load a new one the previous one is deleted...

Answer 1

[Thomas]

Since you are saving all the variables a 'z' try the following..

Z_1=load('C\wherever.the.variable.is.stored\Z_1');
Z_2=load('C\wherever.the.variable.is.stored\Z_2');
Z_3=load('C\wherever.the.variable.is.stored\Z_3');

total=Z_1.z+Z_2.z+Z_3.z

or

load('C\wherever.the.variable.is.stored\Z_1');
Z_1=z;
load('C\wherever.the.variable.is.stored\Z_2');
Z_2=z;
.
.
total=Z_1+Z_2...

[Guillermo Lopez]

But wouldn't the second option erase every time the previous z value?? I mean if you are saying that Z_1=z and then Z_2 is z then how can they both be z????

[Jan]

Using LOAD without catching the output stores the variable z in the current workspace. "Z_1=z" copies the value of "z" to the variable "Z_1". If the next MAT file is loaded, the value of "z" is overwritten, but the copy in "Z_1" is still ok. Clearer now?

[Thomas]

As Jan explained,, every time you load a new file the variable z is put in Z_1 and Z_2 and so on and not lost..

Did you try option 1?

[Guillermo Lopez]

Ok I get it now. I will try this...

Answer 2

[Honglei Chen]

The first variable in save is the file name, not the variable name. So in each of your files, the variable name is still z. Therefore, after you load all the files, there is still only one z. To do what you want, you need to save those files using different variable name z1,|z2|,... or you load them to a variable like this

load('C\wherever.the.variable.is.stored\Z_1');
Z_1 = z;
load('C\wherever.the.variable.is.stored\Z_2');
Z_2 = z;
load('C\wherever.the.variable.is.stored\Z_3');
Z_3 = z;

TotalZ=Z_1+Z_2+Z_3;

[Guillermo Lopez]

How can I save the variable I want (z) with different variable names each time it loops??

[Walter Roberson]

Dynamic structure field names, and save() with the -struct option.

[Honglei Chen]

eval(['Z_' num2str(v) '=z']);

save(['Z_' num2str(v)],['Z_' num2str(v)])

[Walter Roberson]

Using eval() is not recommended!!