Re: Create Structure

[Sergei Steshenko]

>________________________________
> From: Thomas D. Dean <address@hidden>
>To: Octave Help <address@hidden> 
>Sent: Sunday, June 12, 2016 9:51 AM
>Subject: Create Structure
> 
>
>I have a character array with 156 names and a corresponding array of values;
>
>octave:341> a=["n1";"n2";"n3"]
>octave:342> b=[1;2;3]
>octave:343> x=struct(a(1,1:2),b(1),a(2,1:2),b(2),a(3,1:2),b(3))
>octave:344> x
>x =
>
>   scalar structure containing the fields:
>
>     n1 =  1
>     n2 =  2
>     n3 =  3
>
>Is there a function to do this?  Do I have to go to an oct file?
>
>I have looked at cellfun, and structfun, but, could not make either 
>work.  Most likely, I do not understand this...
>
>Tom Dean
>
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>Help-octave mailing list
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>
>


"Is there a function to do this?"  -several years ago I wrote a function which 
allows to create a structure from a list of key -> value pairs as its argument:

cat -n consistent_struct.m
1  function os = consistent_struct(varargin)
2    if(rem(length(varargin),2))
3      error("there must be even number of input arguments");
4    endif
5
6    os = [];
7    for struct_field_number = 1:2:length(varargin)
8      #fprintf(stderr, "key: %s\n", varargin{struct_field_number});
9      key = varargin{struct_field_number}; # no check of 'key' correctness is 
performed
10      val = varargin{struct_field_number + 1};
11      os = setfield(os, key, val);
12    endfor
13  endfunction
14
15  # testcase for Yury T - assuming Yuri wants to access things by "file1*.dat"
16
17  par1_1=1;
18  par2_1=2;
19  par1_2=3;
20  par2_2=4;
21
22  name = consistent_struct\
23           (
24           "file1.dat", {par1_1, par2_1, "ID1"},
25           "file2.dat", {par1_2, par2_2, "ID2"}
26           );
27
28
29
30  getfield(name, "file2.dat"){1}
31  getfield(name, "file2.dat"){1, 1}
32  # pay attention - the above two lines produce the same output - 2 * crap !!
33
34  getfield(name, "file2.dat"){2}
35  getfield(name, "file2.dat"){1, 2}
36  # pay attention - the above two lines produce the same output - 2 * crap !!
37
38  getfield(name, "file2.dat"){3}
39  getfield(name, "file2.dat"){1, 3}
40  # pay attention - the above two lines produce the same output - 2 * crap !!
41
42
43  name
44  # pay attention - _two_ indices (like [1,2]) are printed - 2 * crap !!
45

.

And here is what the test case produces:

"

octave:1> source("consistent_struct.m");
ans =  3
ans =  3
ans =  4
ans =  4
ans = ID2
ans = ID2
name =

scalar structure containing the fields:

file1.dat = 
{
[1,1] =  1
[1,2] =  2
[1,3] = ID1
}
file2.dat = 
{
[1,1] =  3
[1,2] =  4
[1,3] = ID2
}

octave:2>
"
- this was tested on octave-3.6.4.

Octave (and probably Matlab - I don't have Matlab to test) indexing is crap, 
but it's a separate issue.

The test case shows that value can be a hierarchical data structure - in this 
case anonymous cell array.
...
Indentation got screwed by the Email client, so I'm attaching the function too.


--Sergei.

consistent_struct.m
Description: Text Data