How to create dynamic field reference in a structure

Hi,

I am trying to read lines from a text file generated during a simulation. For ex

Text file has information as follows

$------------------------------------------------------------------------REQUEST

[REQUEST]

 NAME    =  'driver_demands'

 ID      =  1
 X           =  'steering'
 Y           =  'throttle'
 Z           =  'brake'
 R1          =  'gear_position'
 R2          =  'clutch'
 X_UNITS     =  'angle'
 Z_UNITS     =  'force'
$------------------------------------------------------------------------REQUEST
[REQUEST]
 NAME    =  'sse_outputs'
 ID      =  2
 X           =  'yaw_moment'
 Y           =  'lateral_force'
 X_UNITS     =  'torque'
 Y_UNITS     =  'force'
$------------------------------------------------------------------------REQUEST

I would like to create a structure with dynamic field names. Req.info is a structure with 4 fields ID, NAME, Marker_Data, Complete_Data

I would like to update Req.info Such that Req.info(1).Complete_Data =

       NAME: 'driver_demands'
         ID: 1
          X: 'steering'
          Y: 'throttle'
          Z: 'brake'
         R1: 'gear_position'
         R2: 'clutch'
    X_UNITS: 'angle'
    Z_UNITS: 'force'

Where

Req.info(1).Complete_Data.X

Req.info(1).Complete_Data.Y

Req.info(1).Complete_Data.Z... (Fields X,Y,Z,.... are created dynamically)

Such that Req.info(1).Complete_Data.X = steering and so on...

I have tried with following code but could not succeed.

while ~strncmp(zeile,'$', 1)

        line = fgetl(fid);
        [Marker_name, Marker_data]= strread(line, '%s''%s', 'delimiter','=');
        Marker_name = strtrim(Marker_name);
        Marker_data = strtrim(Marker_data);
        Marker_data = Marker_data (1:end-1);
        eval(['Req.info(', num2str(i), ').Complete_Data.', char(Marker_name), ' = ', char(Marker_name), ';']);
    end

This is the first time am dealing with data import functions. Please help me out..

Thanx a lot..

Answer 1

[Jan]

Perhaps Marker_Name is a scalar cell string, then:

Req.info(i).Complete_Data.(Marker_name{1}) = Marker_data;

[Udayteja]

Thanx a lot...:)

Now the code runs giving following result

Req.info(1).Complete_Data

ans =

X: {'steering''}

Y: {'throttle''}

Z: {'brake''}

R1: {'gear_position''}

R2: {'clutch''}

X_UNITS: {'angle''}

Z_UNITS: {'force''}

but I do not understand the significance of flower braces here. what do you mean by scalar cell string. How can I change the result such that I do not get the Flower braces and an additional ' at the end of each line?

[Walter Roberson]

Req.info(i).Complete_Data.(Marker_name{1}) = Marker_data{1};

[Udayteja]

Hi,

After certain iterations the program stops with the following error.

Index exceeds matrix dimensions.

Is there a way i could increase the size?

[Walter Roberson]

"index exceeds matrix dimensions" is always a programming error, not a problem with the size being too small.

The first thing I would check at that point is whether at some point the strread() is returning empty cell arrays -- if it was then element {1} would exceed the dimensions of the array.

Answer 2

[Walter Roberson]

Req.info(i).Complete_Data.(Marker_name) = Marker_data;

[Udayteja]

Thanq for your reply. But even this is showing an error.

??? Argument to dynamic structure reference must evaluate to a valid field name.

[Walter Roberson]

At the line before that,

fprintf(1, '|%s|\n', Marker_name);

length(Marker_name)

and check to see whether Marker_name has any blanks or any characters other than A-Z, a-z, 0-9, and underscore. If it has any of those, then it is not a valid name for a structure field.