Merge same field of 36 structures

I want to merge same field (e.g., long which is a matrix) from 36 structures of lenghth (266) which has 20 fields for each structure For example, I have structures S1, S2, S3, S4, S4 ... S36 etc of length varying between 266 to 306 with same field names lat, long, date, temp, air etc which are matrices of variable length varying from [1500 to 15000 by 7]. I want to merge S1 to S36 of field "long" and "date", i.e., S = [S1.long, S2.long, ...].The error I receive for the below code is, "Reference to non-existent field 'long'.

numfiles = length(filenames);
results = cell(numfiles, 1);
U1 =[];
for K = 1 : numfiles
   thisfile = filenames{K};
   datastruct = load(thisfile);
    xyz = datastruct.long;     %extract particular variable
   processed_xyz = vertcat(U1,xyz);  %call appropriate function to handle the data
   results{K} = processed_xyz;
end

This is suggested by a matlab user, however when I implement it it does not recognize the long field in the datastruct structure.

[Jan]

What does "merge" mean? What exactly is the wanted output? What does "it it does not recognize the long field" mean? Do you get an error message? Then please be so kind to share it with trhe readers. We cannot run the code due to the lack of inputs.

vertcat(U1,xyz) is free of use, when U1 is the empty matrix []. Please take the time to explain, which class and size the inputs are, and what do you want as output. The current code can be abbreviated:

numfiles = length(filenames);
results  = cell(numfiles, 1);
for K = 1 : numfiles
   datastruct = load(filenames{K});
   results{K} = datastruct.long;
end

[per isakson]

Maybe you want to try to fix your code with the help of: Debug a MATLAB Program and Examine Values While Debugging

[per isakson]

Did you try

xyz = datastruct.S1.long;

Did you inspect datastruct in the Variable Editor?

[nlm]

This works,

xyz = datastruct.S1.long;

However, I want to run it in loop for 36 STRUCTURES.

Answer 1

[per isakson]

Try this

%%
numfiles = length(filenames);
results = cell(numfiles, 1);
for K = 1 : numfiles
    datastruct = load( filenames{K} );
    U1 = zero( 0, 7 );
    for jj = 1 : 36
        U1 = vertcat( U1, datastruct.(sprintf('S%d',jj)).long );  %#ok<AGROW>
    end
    results{K} = U1;
end

And see: TUTORIAL: Why Variables Should Not Be Named Dynamically

[nlm]

I get an error as "Reference to non-existent field S"

[per isakson]

Not with my code, I assume

>> jj = 35;
>> sprintf('S%d',jj)
ans =
    'S35'    

What code throws that error?

Maybe you want to try to fix your code with the help of: Debug a MATLAB Program and Examine Values While Debugging

[nlm]

%%
files = length(filenames);
results = cell(numfiles, 1);
for K = 1 : numfiles
    datastruct = load( filenames{K} );
    U1 = zero( 0, 7 );
    for jj = 1 : 36
        U1 = vertcat( U1, datastruct.(sprintf('S%d',jj)).long );  %#ok<AGROW>
    end
    results{K} = U1;
end

The datastruct loads only one structure, and not all the structures in the folder. why is that ? Though filenames{K} is a cell of length 36

[per isakson]

What does

S = whos( '-file', filenames{1} )

output?

"Reference to non-existent field S" Report the full error message

"why is that" read the documentatio n on load

"Though filenames{K} is a cell of length 36" No, it's the name of a file.

[nlm]

whos( '-file', filenames{1} )

Name Size Bytes Class Attributes

S1 248x1 10140287550 struct

"Reference to non-existent field S" This is the full message

"why is that" read the documentation on load : I'll refer

"Though filenames{K} is a cell of length 36" : Yes it is the name of the file, I meant length of K

[per isakson]

I now assume that

whos( '-file', filenames{2} )

will output S2, et cetera

"This is the full message" IMO: it's much easier to debug functions than scripts.

I assume that the error was caused by jj being empty

>> jj = [];
>> sprintf('S%d',jj)
ans =
    'S'

[per isakson]

Maybe, this works

function    results = ccsm( filenames )
    %%
    numfiles = length(filenames);
    results = cell(numfiles, 1);
    for K = 1 : numfiles
        datastruct = load( filenames{K} );
        U1 = zero( 0, 7 );
        for jj = 1 : length( datastruct.(sprintf('S%d',K) ) )
            U1 = vertcat( U1, datastruct.(sprintf('S%d',K))(jj).long );  %#ok<AGROW>
        end
        results{K} = U1;
    end
end