How to load data from Octave?

I have a .M file from Octave that I want to run in MATLAB, but I obtain an error. Here is the content of .M file (it's just one line):

load "Slovenia_centered.mat"

And here is the error:

Error using load
Unable to read file '"Slovenia_centered.mat"': Invalid argument.

Error in 
Slovenia_centered (line 1)
load "Slovenia_centered.mat"
^^^^

Answer 1

[dpb]

d=dir('Slovenia_centered.mat')

d = struct with fields:
       name: 'Slovenia_centered.mat'
     folder: '/users/mss.system.hwgbc'
       date: '13-Feb-2026 16:09:15'
      bytes: 8972
      isdir: 0
    datenum: 7.4003e+05

type Slovenia_centered.mat

 2.43585211e-01
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Aha! It's text, not native .mat.

x=load('-ascii','Slovenia_centered.mat')

x = 545×1

0.2436 0.0434 -0.1123 -0.2285 -0.1911 -0.2707 -0.3114 -0.3503 -0.0665 -0.0091 -0.0821 -0.1782 -0.2971 -0.2469 -0.2194

<mw-icon class=""></mw-icon>

<mw-icon class=""></mw-icon>

To write data from Octave to be imported into MATLAB, it would be more portable to either explicitly write text data with fprintf or whatever other higher-level functions Octave has implemented in parallel with MATLAB or as native binary data with fwrite to read with fopen and fread

Although, presuming Octave has it implemented, if it can write a specific version of a .mat file that has the benefit of also storing the variables and shape and type information that alternate forms don't without extra effort. Just have to be sure to write in a known version and then verify it does work as expected (not that I have any reason to think it wouldn't; Octave has been around for a long time).

[Svit]

Thank you so much dpb. One further question. I need the data not in one column, but in five columns, such as in the attached file Slovenia. The data include observations of five variables: consumption, investment, interest rates, inflation rate and monetary aggregate M3. How could I split the data in multiple columns? I searched the questions on this forum, as well as on Google and AI (Copilot), but I haven't found anything useful.

My code looks like this, it includes temp variable that includes five types of data:

temp = [ data];
Dataslpiobs=temp(:,1);
Dataslinobs=temp(:,2);
Dataslcobs=temp(:,3);
Dataslrobs=temp(:,4);
Dataslmobs=temp(:,5);

Your help is much appreaciated!

[dpb]

I moved to continue the same thread -- dpb

That depends on how the data were written...let's see what the file actually contains...

%type Slovenia
Slovenia
whos

  Name               Size            Bytes  Class     Attributes

  Dataslcobs       109x1               872  double              
  Dataslinobs      109x1               872  double              
  Dataslmobs       109x1               872  double              
  Dataslpiobs      109x1               872  double              
  Dataslrobs       109x1               872  double              
  ans                1x34               68  char                
  temp             109x5              4360  double              

Well, we have an array and the others that were created from them. OK, now see what was mentioned in the comment...

Presuming you know a prior the variable names to use, then you can more directly convert to a table from the 2D array as

vnames={'Dataslcobs','Dataslinobs','Dataslmobs','Dataslpiobs','Dataslrobs'};
tData=array2table(temp,'VariableNames',vnames);
head(tData)

    Dataslcobs    Dataslinobs    Dataslmobs    Dataslpiobs    Dataslrobs
    __________    ___________    __________    ___________    __________

      0.067         0.037379       0.18434       31.625         0.11012 
      0.039        -0.098394     -0.015834        16.43        0.072263 
      0.042         -0.20897       -0.1716       17.254        0.014422 
       0.06         -0.29284      -0.28771       28.034       -0.032916 
      0.039         -0.10147      -0.25037       19.002       0.0049062 
      0.047         -0.20429      -0.32994       18.277       -0.054305 
      0.037          -0.2644      -0.37067       16.178       -0.078131 
      0.046         -0.31964      -0.40951       21.855        -0.11888 

However, here's no reason to make/have two copies of the same data; if you have a (again text) .mat file that is the variables as a single array, then you can read it into the table directly as

fn='OctaveArrayDataFile.mat';   % assume text file
tData=readtable(fn,'FileType','text','VariableNames',vnames);

where like with load have to tell MATLAB a .mat file is in text format rather than native form and it is again required to know the variable names to use (and in which order they are in the 2D array) from prior knowledge

You can then apply all the power of MATLAB to the table referencing each by name with whatever it is that is wanted to be done.

The underlying Q? is how are you getting these .mat files -- are you creating them yourself or is somebody providing them? Can you (or they) change how they're being written to save as -V7 MATLAB .mat files in which case you'll get the variable names and sizes automagically?

What specifically is to be done might aid in other more specific recommenations.

[Svit]

1. I think I can't use command fn='OctaveArrayDataFile.mat';, because I obtain error:

Error using readtable (line 19)

Ambiguous parameter name: VariableNames.

I assume I have to substitute name 'OctaveArrayDataFile.mat' with an actual name of my .MAT file, i.e. fn='Slovenia_centered.mat';? Even if I don't do the substitution, I obtain the same error code...perhaps the file isn't a text file?

2. I created the .MAT file from existing Slovenia.m file using Octave's commands for demeaning (deducting means) for all 5 variables: Dataslrobs=center(Dataslrobs) (repeating this five times for all 5 variables) and then "save -ascii Slovenia_centered.mat Dataslcobs Dataslinobs Dataslmobs Dataslrobs Dataslpiobs" in order to save the result. The original .M file was provided to me by users of Dynare forum.

3. The reason I need the temp variable, that contains the 5 variables, is that I need them for my Dynare's .MOD file, that includes references to 5 variables. I can't upload .MOD file here because the format isn't supported, so I converted it into a .TXT file, please find it attached.

Thank you.

[dpb]

"I think I can't use command fn='OctaveArrayDataFile.mat';,"

Yeah, I forgot that one can't name variables in the readtable function call.

" I need the temp variable, that contains the 5 variables,..."

But, there's a problem here in that the file is just one list of values -- how was the temp array constructed--by knowing a priori that the file is supposed to contain exactly five variables, I presume?

I had thought when you showed that m-file that the file had been arranged such that the temp array was being read as the 2D array and wo the file itsel had five columns. Unless there are other files, that isn't true and so the previous assumptions all are in error.

d=dir('Slov*cent*.mat');     % get a dir() for the file(s) 
fn=d.name;                   % the name without having to type long name <vbg>
load('-ascii',d.name)
whos

  Name                     Size            Bytes  Class     Attributes

  Slovenia_centered      545x1              4360  double              
  ans                      1x45               90  char                
  d                        1x1               960  struct              
  fn                       1x21               42  char                

So, what is obtained after the load is, indeed, just one long vector so

temp=reshape(Slovenia_centered,[],5);   % reshape to 2D presuming are 5 variables
whos

  Name                     Size            Bytes  Class     Attributes

  Slovenia_centered      545x1              4360  double              
  ans                      1x45               90  char                
  d                        1x1               960  struct              
  fn                       1x21               42  char                
  temp                   109x5              4360  double              

In this case, there actually are 109 rows of 5 elements each, not precisely 500 as the prior code produced. You'll have to decide which 9 are immaterial to throw away or keep them all; we have no way to know.

You already have the code to create separately named variables from the array given you know what names you want. With the 1D vector of just numeric values, there really isn't any more effective way to take the next step. One ugly coding way that is not recommended to "poof" variables into the workspace is eval, but as the following shows, that's ugly and very error prone and difficult to debug as well as being slow---but that said,

vnames={'Dataslcobs','Dataslinobs','Dataslmobs','Dataslpiobs','Dataslrobs'};
for i=1:numel(vnames)
  cmd=sprintf('%s=temp(:,i);',vnames{i});   % make a command to execute
  eval(cmd);                                % and evaluate the string
end
whos D*                                     % see who we made

  Name               Size            Bytes  Class     Attributes

  Dataslcobs       109x1               872  double              
  Dataslinobs      109x1               872  double              
  Dataslmobs       109x1               872  double              
  Dataslpiobs      109x1               872  double              
  Dataslrobs       109x1               872  double              

return

As noted before, if you would use the option in Octave to write a compatible -V7 .mat file, then you could load exactly what you have in Octave into MATLAB as the five variables as those named variables in the one load command. But, as is, the variable names aren't in the file and it's just a 1D text vector.

% OCTAVE CODE snippet...
Dataslrobs=center(Dataslrobs);
...
save -V7 Slovenia_centered.mat Dataslcobs Dataslinobs Dataslmobs Dataslrobs Dataslpiobs

should do the trick presuming Octave really does implement the MATLAB -mat file correctly. Then just

% MATLAB code
load Slovenia_centered.mat

should give you back the five variables. I haven't had an install of Octave in 20 years so can't test locally, but it's supposed to work.

The other Q? then becomes, if you have access to MATLAB to read these files, why are you creating them with Octave instead of MATLAB to begin with? MATLAB can do everything Octave can do without the hassle. You might have to fix a few syntax errors if somebody used some of the Octave peculiarities that MATLAB doesn't, but it shouldn't be bad.

There's nothing preventing you from just using the existing script to read the temp array and manually create the five specific variables from the array. Given the way the present Octave script is writing it as a 1D text array without headers, that's about the best that can be done if you aren't going to change the way Octave writes the data (or just forget Octave and do it in MATLAB to begin with).

[Stephen23]

"I created the .MAT file from existing Slovenia.m file using Octave's commands for demeaning (deducting means) for all 5 variables: Dataslrobs=center(Dataslrobs) (repeating this five times for all 5 variables) and then "save -ascii Slovenia_centered.mat Dataslcobs Dataslinobs Dataslmobs Dataslrobs Dataslpiobs" in order to save the result"

Then why not save yourself all of this trouble by saving using the option -V7 ?

https://octave.sourceforge.io/octave/function/save.html

Converting your data to text and back again is a superfluous indirection. Use a binary file format!

Answer 2

[dpb]

load "Slovenia_centered.mat"

Using the command syntax the filename is text already so it's including the apostrophes as well...try

load Slovenia_centered.mat

I'm not sure about what level for .mat file compatibility Octave supports, you may need to check there about ensuring .mat files.

[Stephen23]

Yes. The documentation explains why using double quotes will fail with command syntax, it has whole section entitled "Why Does Using Command Form With Strings Return An Error?":

https://www.mathworks.com/help/matlab/matlab_prog/frequently-asked-questions-about-string-arrays.html#mw_c5847aac-8745-4fb1-997a-4fc5c324fffb

The gist of it is "In command form, double quotes are treated as part of the literal text rather than as the string construction operator". This is to be consistent with how command syntax has always worked.

[dpb]

BTW, to complete the picture

load("Slovenia_centered.mat")

will also work because as an argument the "" are constructors and the underlying char string will be passed.

[Stephen23]

According to the Octave SAVE documentation

https://octave.sourceforge.io/octave/function/save.html

its default is to "Save the data in Octave’s text data format. (default)." Apparently it also has options to save in formats which are MATLAB compatible.