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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 -1.91116589e-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 so the file itself had five columns. Unless there are other files, that isn't true and so the previous assumptions all are in error.

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

try
  assert(mod(Slovenia_centered,5)==0)   % make sure is divisible by 5
catch
  error('Vector length (%d) not compatible; unable reshape to 5 variables.  Aborting.', ...
         numel(Slovenia_centered))
end
Slovenia_centered=reshape(Slovenia_centered,[],5);   % reshape to 2D presuming are 5 variables
whos

  Name                     Size            Bytes  Class     Attributes

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

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. NOTA BENE: the above just reshapes the same variable in place, doing away with the temp arrray and includes a check that the vector length is divisible by 5.

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=Slovenia_centered(:,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              % just in here so online "run" won't error on next lines

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 vector 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!

[Svit]

The reason I produced these files in Octave is that I had no access to MATLAB before. I purchased it now and now I plan to use MATLAB only.

Thank you very much for the code, the first part works just fine, but the following part produces an error:

try

assert(mod(Slovenia_centered,5)==0) % make sure is divisible by 5

catch

error('Vector length (%d') not compatible; unable mae to 5 variables. Aborting.', ...

numel(Slovenia_centered,5))

end

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

whos

The error:

error('Vector length (%d') not compatible; unable mae to 5 variables. Aborting.', ...

↑

Invalid expression. Check for missing multiplication operator, missing or unbalanced delimiters, or other syntax error. To construct matrices, use brackets

instead of parentheses.

[Stephen23]

If you require that single quote after the integer:

'Vector length (%d'') not compatible; unable mae to 5 variables.  Aborting.'
%                 ^^

Otherwise:

'Vector length (%d) not compatible; unable mae to 5 variables.  Aborting.'

[dpb]

Problem with trying to edit inline in the forum without syntax checking in place...changed horses in mid-stream about adding the message in the assert call to separate catch clause and didn't catch all the fixups needed including the dangling quote.

What I really intended was something more on the order of

error('Vector length (%d) not compatible; unable reshape to 5 variables.  Aborting.', ...
         numel(Slovenia_centered))

There was also a leftover ",5"" from the initial mod() operation pasted in plus a typo in the error message text itself.

"...now I plan to use MATLAB only."

You'll probably find that a good decision in the long run.

I'll note in doing so that earlier you mentioned "demeaning (deducting means) for all 5 variables: Dataslrobs=center(Dataslrobs) (repeating this five times for all 5 variables) ".. Note that in MATLAB (and Octave, too, for that matter) virtually all builtin functions operate by column so it isn't necessary to either loop or duplicate variable names in such a fashion; it's a general sign of not using the vector ability of MATLAB effectively. Instead, use arrays and if need to identify columns in the array, use the table or named fields in a structure; these can be easily manipulated programmatically with direct code to address them rather than having to use contorted features such as eval or duplicate code lines multiple times to operate on the data. Although MATLAB does not explicitly incorporate the center function, it uses

s_c=detrend(s,0);   % remove best 0-order trend (mean) from array s by column

The above is identical to

s_c=s=mean(s);

and, of course, if the mean isn't of interest, one can always just replace the original data in place and if wanted, keep the means in another array.

m=mean(s);      % compute means of s
s=s-m;          % remove means, keeping their values if want later

Of course, one could add their own(*) center function via a user m-file or via an anonymous function...

center=@(a)a-mean(a);  % anon function center

although one can't support the optional dim argument that way.

(*) As a personal use pattern, besides a default Work directory I create an Utilities folder in which I keep such generally useful functions that aren't (yet) built into MATLAB. I permanently add these two folers at the top of the MATLAB path so anything in Work, then Utilities is called first.

If I have a specific piece of work for a given client or job, I create its own folder and have a pattern for setting a work environment that will save the current default path and then move to the other environment incorporating any other specific pieces needed for it. These uniformly also rely on the Utilites being available. I can then use the optional input parameter with a value of 'quit' to exit that location and return to the base Work location. That has been most helpful working model to keep things localized but have a common toolset available regardless.

[Svit]

Thank you very much for the code, I will use the vector ability of MATLAB from now on!

But you said I have to make sure the number is divisible by 5. However the following code produces an error, although 545 is divisible by 5. Code:

try

assert(mod(Slovenia_centered,5)==0) % make sure is divisible by 5

catch

error('Vector length (%d) not compatible; unable reshape to 5 variables. Aborting.', ...

numel(Slovenia_centered))

end

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

whos

Error:

Vector length (545) not compatible; unable reshape to 5 variables. Aborting.

[dpb]

You need to double-check on me, too...in that code the numel() call to get the length is missing......

Slovenia_centered=randn(545,1);
assert(mod(numel(Slovenia_centered),5)==0)
disp('Done')

Done

Runs w/o throwing error...

[Svit]

I hope I will be as great MATLAB programmer as you one day :D.

Okay, so the following code now works perfectly:

%type Slovenia
Slovenia
whos

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

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

try
    assert(mod(numel(Slovenia_centered),5)==0)
catch
    error('Vector length (%d) not compatible; unable reshape to 5 variables.  Aborting.', ...
        numel(Slovenia_centered))
end
Slovenia_centered=reshape(Slovenia_centered,[],5);   % reshape to 2D presuming are 5 variables
whos

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

return              % just in here so online "run" won't error on next lines

Finally, I assume the obtained data in 5 columns is now saved in file Slovenia_centered.mat, right? I mean, using "load Slovenia_centered.mat" I obtain another error, and also my computer shows the last change to both Slovenia_centered.mat and Slovenia_centered.m were made weeks ago... the error:

Error using load
Unable to read file 'C:\[censored]\Slovenia_centered.mat'.

[dpb]

You've copied all the example code inserted just to show what was in the file as well as the actual code to do the work -- including the 'return' line that I commented that was there only so the subsequent example line of code to use in Octave to save the data from it i(Octave) as the five separate variables you had in it.

There's no code in what you ran that will save the ..mat file in MATLAB to then be able to read it.

You have to decide what it is that you're actually trying to do -- read the original Octave-written ASCII formatted file and create the five variables that we started with or build the data in MATLAB to begin with or precisely what are you trying to do now?

As @Stephen23 and I have both noted, if you were to change the save statement in Octave that created the existing file(s) to use -v7 instead of -ascii then you could just load that file in MATLAB and have the same variables by name in MATLAB directly without any other code being needed. But, if you continue to write files in the same way, then you need the code to create the variables the way you want them instead as one long vector. But, then, if you want to create a new .mat file you'll have to SAVE those in MATLAB; it won't somehow magically change the existing file.

The point is, you have to decide what is your objective here from what starting point and write code specific to those aims. You have to decide that; we can't do that for you.

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.