Thank you! I checked and it does not solve the problem.
However I have been thinking and got some insights.
1. In gretl, in preferences we need to specify the executable of Octave and I was linking the exe file.
When I changed it to the bat file, this error message disappeared. So probably it was because I
wrongly specified preferences.
2. But it does not solve the problem. Now the error message is this:
gretl version 2019c
Current session: 2019-07-14 15:17
? open data9-7
Read datafile D:\Programok\gretl\data\ramanathan\data9-7.gdt
periodicity: 4, maxobs: 64
observations range: 1975:1 to 1990:4
Listing 12 variables:
0) const 1) QNC 2) PRICE 3) INCOME 4) PRIME
5) UNEMP 6) STOCK 7) POP 8) WINTER 9) SPRING
10) SUMMER 11) FALL
? matrix xy = { PRIME, UNEMP }
Generated matrix xy
? mwrite(xy, "xy.mat", 1)
? foreign language=Octave
? xy = gretl_loadmat("xy.mat");
? x = xy(:,1);
? y = xy(:,2);
? h = sum(x.*y);
? gretl_export(h, "h.mat");
? end foreign
? h = mread("h.mat", 1)
C:\Users\MAJOR KLÁRA\AppData\Roaming\gretl\h.mat: No such file or directory
And really, gretl_export does not make its task (but does when the script is running in octave GUI). But this is something I am familiar with. The octave can not write any file to disk of which the path has either space or accented character in it. As it is in my case. (At least it was a few versions ago, now the GUI version can handle this. I just checked now: the command line version can not handle accented characters in the path). Therefore any time I work with octave I create a special folder for the project without using system libraries.
So basically I think I know what the problem is and I can not really solve it, unless it will become possible the specify the folder exactly where gretl works (I mean mwrite, mread, gretl_loadmat and gretl_export). Maybe in the future?
Or the other possible solution is if it is possible to write my own gretl_export function for octave and bypass the default version. This in itself would give me the flexibility to handle these kind of difficulties.
Sorry for taking your time, I think the problem is in my system in general.
Thank you again very much,
Klára