How to create dynamic field reference in a structure

2012 6 18
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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..

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Jan
Jan 2012-6-18

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Perhaps Marker_Name is a scalar cell string, then:
Req.info(i).Complete_Data.(Marker_name{1}) = Marker_data;

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Udayteja
Udayteja 2012-6-18
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
Walter Roberson 2012-6-18
Req.info(i).Complete_Data.(Marker_name{1}) = Marker_data{1};
Udayteja
Udayteja 2012-6-18
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
Walter Roberson 2012-6-18
"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.

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Walter Roberson
Walter Roberson 2012-6-18

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

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Udayteja
Udayteja 2012-6-18
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
Walter Roberson 2012-6-18
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.

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